Do you have the agent 4.5 management component checked into the ePO server? (check under software manager is the easiest way now :-) )
Have you tried upgrading this machine to agent 4.6?
this is a bit more complicated than that. This ePO system is firewall separated and cannot see out to the internet. (it has a source repository on another ePO server the latter of which providing the necessary products or the signatures. Therefore Software Manager does not show anything.
It has been working this way for years. Actually we never had to really install products on each clients because they were installed from images. Regardless, some VirusScan upgrades have been done in the past successfully (with earlier ePO server versions).
Also, we successfully are using tasks based on tag assigment on another epo server (4.6 !) with the same agent version as I wrote.
I'd like to have some troubleshooting advice I would not want to install everyting blindly (if possible :-) ).
No problem at all! I think you can view under extensions and then double check the agent management 4.5 is installed. (I say this because when i setup my ePO 4.6.1 I didnt check in anything for HIPS7 which caused some issues!).
and the upgrading a single agent was to rule in or out if its just this agent version.
Also I would recommend upgrading to Agent 4.6 at some point so you can use the 'run click task now' options, it makes life alot easier!