Backup exec uses port 8443

Change this port in SEPM to 8444 or something else check the document below on how to change it
http://service1.symantec.com/SUPPORT/ent-security.nsf/docid/2007111308424148

its showing error   ErrorCode: 0x10010000
run the repair of sepm and then the management server configuration wizard, check if your default app pool is started in IIS.
IIS reset or Reboot of the server, usually fixes the issue. Give it a try.

"Failed to connect to server" message during login and the scm-server-0.log file shows '401 Unauthorized' errors.

http://service1.symantec.com/support/ent-security.nsf/docid/2009073117184848
is your IIS running on IIS 32 or 64 bit

How to switch between the 32-bit versions of ASP.NET 1.1 and the 64-bit version of ASP.NET 2.0 on a 64-bit version of Windows
http://support.microsoft.com/kb/894435

its shows 500
http://support.microsoft.com/kb/311766 

 Check the ODBC configuration

go to
 C:\Windows\SysWOW64\odbcad32.exe

1. On the System DSN tab, double-click SymantecEndpointSecurityDSN
2. Go through the wizard to ensure the following settings:

   Name: SymantecEndpointSecurityDSN
   Description: <Anything>
   Server: Servername\InstanceName (Can be blank as it is localized, otherwise specify the default: sem5)
   Login ID: dba
   Password: <password>

3. Leave the defaults for the rest of the items and click Finish
4. Click Test Data Source , it should return "Success"
5. Click OK

Kumar,

I tried to set-up System DNS - with a success. Though there are some differences from your suggested setting from mine. For instance: I have a remote database server, so I entered that address, valid login id was provided at database server so I entered it also along with custom password - that setup works, the DB connection test returned successful connection/test. I can report, that there is no problem at database connection from SEM server end...

Thats right I missed your SEPM was on SQL..

Well..try repairing SEPM from Add/Remove Programs ( it wouldn't change anything ) 

 Enable logging on reporting and secars in IIS

IIS Manager - Websites- Symantec Web Server - 
right click reporting - properties - log visit same with secars

Try loggin into SEPM to generate logs 
then go to C:\WINDOWS\system32\Logfiles\W3SVCxx

open the latest logs and what http error you get for reporting or secars.

as your current logs say 500 which means either database or IIS ( 32-to-64 bit conversion ) issue.
However since installing of BE shouldn't change that so it shouldn't be a issue.

Kumar,

I tried to modify logging in IIS (it is IIS7) and here are the two responses from loading the root of the Symantec Default Site and requesting secars dir:

#Fields: date time s-sitename s-computername s-ip cs-method cs-uri-stem cs-uri-query s-port cs-username c-ip cs-version cs(User-Agent) cs(Cookie) cs(Referer) cs-host sc-status sc-substatus sc-win32-status sc-bytes cs-bytes time-taken
2010-03-05 20:00:43 W3SVC2 AUXSRV 192.168.1.104 GET / - 8014 - 192.168.1.2 HTTP/1.1 Mozilla/4.0+(compatible;+MSIE+7.0;+Windows+NT+6.1;+Trident/4.0;+SLCC2;+.NET+CLR+2.0.50727;+.NET+CLR+3.5.30729;+.NET+CLR+3.0.30729;+Media+Center+PC+6.0;+Tablet+PC+2.0;+InfoPath.2;+OfficeLiveConnector.1.4;+OfficeLivePatch.1.3) - - auxsrv:8014 403 14 0 132 587 312
2010-03-05 20:03:48 W3SVC2 AUXSRV 192.168.1.104 GET /secars - 8014 - 192.168.1.2 HTTP/1.1 Mozilla/4.0+(compatible;+MSIE+7.0;+Windows+NT+6.1;+Trident/4.0;+SLCC2;+.NET+CLR+2.0.50727;+.NET+CLR+3.5.30729;+.NET+CLR+3.0.30729;+Media+Center+PC+6.0;+Tablet+PC+2.0;+InfoPath.2;+OfficeLiveConnector.1.4;+OfficeLivePatch.1.3) PHPSESSID=dc092fdfbe416e878eb6999e554a5e73 - auxsrv:8014 500 0 193 144 645 234

Also, I find it interesting that the secars and secreg subdirectories are empty - if I view them in IIS Manager...strange, should there not be some files...for instance I tried to load as suggested in some other forum post:
 

/secars/secars.dll hello,secars

without any luck - it 404ed. On the other hand, the reporting subdir loads just fine and after I try to login it just says that the server is down...

 Those directory will be blank.
Might be issue with PHP

In this Doc look for "Verify the version of PHP that SEPM is using "
http://service1.symantec.com/SUPPORT/ent-security.nsf/docid/2008042212582048

 For Secars test

http://<SEPM_Server_IP_or_Machine_Name:Port>/secar...

here port is 8014

OK now - I checked with the php - the version match, I can run the phpinfo file on the reporting sub-page and all.
I tested the server to serve me secars directory and hello command - all without any luck. The server returned error 500 - which is of course internal server. I read somewhere about this but can not remember about what (SEPM specific)...

 This means IIS is set to 32 bit mode on Windows Server 2003 64 bit operating system when installing Symantec Endpoint Protection Manager. 

Java -1 Errors and HTTP 500 errors when connecting to the Symantec Endpoint Protection Manager on a Windows Server 2003 64 bit

http://service1.symantec.com/support/ent-security.nsf/854fa02b4f5013678825731a007d06af/387a93f58eb98c39882573ed007b50f3?OpenDocument

OK this is starting to get annoying - I checked that document, I ran the Enable32bitAppOnWin64 0 and aspnet_regiis.exe -i commands, after that IISRESET - still no luck, still internal server error - I really appreciate your help Kumar (and all others that have joined in) - but I am beginning to think if I should move SEP to another server altogether :S

I did all of the mentioned above - nothing works, still getting -1 error. Also tried to uninstall SEPM, it could not start IISADMIN due to insufficient permission (???), after that I found some interesting approach on installing SEPM here: http://trycatch.be/blogs/pdtit/archive/2009/04/26/issues-when-running-symantec-endpoint-protection-and-symantec-backup-exec-on-the-same-machine-and-how-to-solve-the-issues.aspx, it had a lot of potential - I think that I even managed to get it running, but after iisreset, I think I lost it. After that I caught myself in some weird and I think permanent magic circle of database owner/modifier - so now I can not even successfully finish reconfiguration of the primary SEPM....
Shame, I was SOOO looking forward to this :S
I will try to deal out to install SEPM on other server, probably on Domain Controller - hope, that nothing breaks :S
I really appreciate all your help but I think that I have hit total wall, no way around....just another road I guess...

 Well..Before you try the new server can you run SEP Support Tool
http://www.symantec.com/techsupp/home_homeoffice/products/sep/Sep_SupportTool.exe

Kumar,

I ran the utility that you have provided me with - it outputed all those errors/warnings that we were discussing during this thread. I tried to fix the them by one - after that - still no luck.
Then I got upset...so I uninstalled Manager, and reinstalled it - interestingly enough, it did not mention any security problem like it did earlier today (I posted about that). So I restarted the server, ran the setup wizard - and again - I ran into trouble. The wizard could create the user and the database, strangely it could not connect to it. So I went back with the buttons, and selected existing database, and it was good - the configuring went by without problems - services started and - I can log in SEPM again...tough I will have to manually add clients that are already running SEP - I hope, that I will manage :)

Anyhows - I really Really Really appreciate all your help, especially to you Mr. Kumar - you really got out for me. Sorry, that none of the suggested solutions worked (per-sei) - reinstall did the trick though...I hope that we could learn something from this. Thank you again.

I hope to have such high response quality in the future - I am sure I will need it :)

Great and secure weekend to all!