You should switch to ePO 4.5, Agent 4.5 and VirusScan Enterprise 8.7i patch 2 that support on windows 7 and windows server 2008.
VSE 8.5 and ePO 4.0 supports Windows 2008 as well.
See KB 60975 for support info.
You should use agent 4.0 patch 1 and a slipstreamed installation of vse8.5 that contains at least patch 7.
However, based on the error message you gave, it sounds like a problem connecting to the repository.
Make sure that you have either added the correct firewall exclusions to your windows firewall policy or other firewalls.
Patch all your product and migrate to EPO 4.5 :
Vscan 8.5i p8
Patch 6 Epo 4.0,
Vscan 8.7i p2
please try to set the agent log to show more detail of this error - the reason of which could be within a number of various ones - and retry the operation. see KB58966.