you can download Intelligent Updater from here

http://www.symantec.com/business/security_response/definitions/download/detail.jsp?gid=savce

Run this and check the status.
if it fails to update, check the logs created by intelligent updater

Can u clarify these point..

How many servers you have..?

Do you have latest update in the server..?
If you don't have update in the server you can download the jdb file and update. Then see whether it updates clients.
Even after having Latest update if doesn't work, it may be corrupt.. try to clean the updates, use the following links.
Ref:
https://www-secure.symantec.com/connect/articles/h...

Check the Client server communication.
If you have windows 2K8 check the fire wall.. If its on turn it off and try ...
Ref:
https://www-secure.symantec.com/connect/articles/t...

Try to run Live update in interactive mode, you may find more details...
Ref:
http://service1.symantec.com/SUPPORT/sharedtech.ns...

i have only one server
latest update is on server, infact other clients are correctly updated.
i'm running win2008 on troubleshootig client, but firewall is disabled
i checked and on 25 august (last updats of definitions) i saw that IE8 was installed...may it be the problem?
i'm tying to use the troubleshooting communications problems guide but i can't find Sylink.xml in C:\Program Files\Symantec\Symantec Endpoint Protection Manager\data\outbox\agent\, there are files with this name only in the subfoldes (with very long alphanumerical names) of that directory, and i don't know witch one to get...

All those Long Alphanumeric folders represent a Group of your SEPM.

Say if you want Sylink.xml for Default group then Login to SEPM - Clients- highligh Default -Click on Details ( from Clients,Policies,Details,Install Package)
you will see your policy serial number just check the first 4 digit of the Pol. Serial Number then find the folder starting with digits in agent folder and then copy the sylink.xml from that folder.
You can also open the profile.xml in the Alphanumberic folder even that tells you which group it belongs to.

i have updated using intelligent updater, and i have copied the correct sylink.xml in sep folder. now i'll see if it starts gaining automatically updates again or not...

You can get the Sylink.xml file from SEPM console also..

Right click on the any group select "export communication settings" select path and mode. It wil create a xml file.

anyone could have a root cause on this issue? I am having the same problem, why sep client after installation and after few days the communication between sepm and sep client was disconnected, some kind of a weird problem

it still doesn' work. Now it doesn't tell me that definiotions are out of date but there is a new revision (installed revision 32, actual = revision 55) and all the clients have got it except this one...so i think the problem is still there...and i can't  follow the guide cause Steps to  edit the SYSTEM account proxy settings through using a Scheduled Task: doesn't work anymore as it doesn't let me run interactive tasks using system account

it is a virtual machine, so i'm using hyper-v manager to connect to it...

Since you were able to get Defs other than AV, There are chances that AV defs got corrupted and sometimes IU can fix this.
Since you have the latest defs now, you might have the issue solved.
:)

no no, it itsn't solved, it stial hasn't downloaded latest definitions from manager server...

I looked through the sylink log.

I found

09/09 06:00:16 [1660] <SendRegistrationRequest:>SMS return=468
09/09 06:00:16 [1660] <ParseHTTPStatusCode:>468=>468 Request not allowed

could you please tell me which version of sep is insatlled?

also you may have look to this :

http://service1.symantec.com/SUPPORT/ent-security.nsf/docid/2008103009471548

Try this

How to clear out corrupted definitions for a Symantec Endpoint Protection Client at

http://service1.symantec.com/SUPPORT/ent-security....

Title: 'Using the "Rx4DefsSEP" utility'
Document ID: 2009032409384048
> Web URL: http://service1.symantec.com/support/ent-security.nsf/docid/2009032409384048?Open&seg=ent

version is 11.0.4000.2295
i'll try it

Admittedly a voo-doo cure, here, but I've posted voo-doo cures here before and they've been marked as The Solution. You never know where your next 25 Connect Points are going to come from, so FWIW...

We had the same situation. One SEP client absolutely would not update virus defs (Only AV is installed. This was a server, so I don't know about TrueScan.) Tried a lot of the same things you've tried, including suggestions posted here.

And opened a support case with Symantec. Burned a BUNCH of time on that, of course, but nothing changed. And then--

--I discovered that another Symantec product, Backup Exec for Windows Servers 12.5's Remote Agent, was failing on this machine. Uninstalled, reinstalled, and patched to the latest of (many) RAWS patches. And not only did RAWS work, SEP immediately started working again, too, all by itself!. And then I realized that the problem was RAWS. Don't know how or why, but that doesn't matter so much.

Reported my findings to Symantec, with the caveat that I wanted to monitor it for a few days. They IMMEDIATELY closed the case without asking for my consent. I admit, that annoyed me a bit, and still does. But in the end it was OK, I guess, because it turned out it really WAS fixed by messing with RAWS. SEP hasn't missed a definition since.

So if you have RAWS installed on this machine, mayve even if it's working, as ours was intermittantly, consider removing RAWS and reinstalling it.

HTH

Yep, on that machine is installed backup exec system recovery for windows, not only the agent but the manager too...i had a very few time today, tommorrow i'll try all this suggestions...

I would suggest going through these two documents in full to be sure full content delivery communication is in order:

•  Troubleshooting Content Delivery to the Symantec Endpoint Protection client
  http://service1.symantec.com/SUPPORT/ent-security.nsf/docid/2008092511045348
   
• LiveUpdate and content troubleshooting for the Symantec Endpoint Protection Manager
  http://service1.symantec.com/SUPPORT/ent-security.nsf/docid/2008091613592648