Hi julian0 first thing you should have a look at are the extensions for VirusScan.
If you go under menu->Software->Extensions wich version do you have for VirusScan Enterprise (it should be 8.5.x, 8.7.x and 8.8.x)
everything is here, installed and running
8.5,8.7 and 8.8
You must know if the repository of these machines is available for them to update their content. You must check if these machine actually has both agent and anti-virus running.
The first test you want to do is try to manually update them. What's the error do you get?
One interesting thing to do is check the last communication for these computers, and what DAT version they have. If all have the same DAT version, is probably something with the repository. If not, several of them may not have anti-virus or agent installed.
Another I'd check is if these machines still exists on your network, if your ePO has no cleanup schedule of inactive agents you must have some old machines that doesn't exist anymore but weren't removed from ePO.
Hope it helps!
Which compliance query are you running?
Agent Compliance, VSE 8.5 Compliance, VSE 8.7 Compliance or VSE 8.8 Compliance.
If you're running the 8.8 compliance query then all computers with 8.5 or 8.7 installed will show up as non-compliant (and vice versa)
Also if you're DAT are out of date this will list machines as non-compliant as well.
I have noticed as well if you've got 8.8 patch 1 installed the sometimes the 8.8 compliance query has a 'Patch = 0' filter on it which can also screw things up.