is it happening on all the box?
on one machine
go to start - run
find sep_inst.log
look for return value 3
paste 15 lines above and below of it.
are these win7 servers?

Install first Liveupdate and try to install SEP after that...

pass on the sep_inst.log file, it can be found under %temp% folder

 Attach Logs of Two Machines.....  & Operating system  is windows XP 

1SEP_INST.LOG
2SEP_INST.LOG

....

I think some virus is present in your PCs which is preventing antivirus to install.
In one pc remove it from network scan with NSS Tool
refer below comment
download NSS and SCAN..
https://www-secure.symantec.com/connect/forums/err...

Hello,

base on the log:
 PROPERTY CHANGE: Adding Original Database property. Its value is '\\70.11.0.43\Symantec Client Pack\Desktops_32-bit\Symantec AntiVirus.msi'.

Do you install SEP from a remote share?

I will invite you to copy locale the package first and test again.

can you try installing locally on the said OS after uninstalling the traces of earlier installed SEP client?

Hi,
Are you install on 64bits or 32 bits client?

Let me tell you ..  

I had two Antivirus Server with OS windows 2003 32 bit. On both server SEP 11.5 antivirus is install.

When i am running SEP client from first server ,client are able to install where as after removing the same from same  client my SEP client are rolling back... one more thing i had check the same by installing first also but  rolling back.

In this issue as per my knowledge two possibilities are there.
1. Virus present in the pc
2.The package which you are using is corrupt... 

One question.Why you uninstalled the SEP?

There are two different location & both location has their on antivirus server.... I tried client package by creating 3 -4 times  than how should it be corrupt..

 Check for the virus possibility...
the reason for uninstalling SEP?

 Where should be virus possibility ..... server or client .....

it can be on the machine where sep is rolling back.
when you are upgrading the client to MU5
do not uninstall the earlier one, just try installing on top of it.
did you try rebooting one client before running the Setup.?

 I am not upgrading to SEP , this is fresh machine on which SEP client is getting install  from one SEP server whereas  from another SEP server is it rolling back ..

Lisa
whats the diff between two servers?

 Nothing only location are different....rest else same