There are two possibilities here. Either the machines aren't remorting the right information, or you have duplicate/orphaned nodes in your system tree reporting old dats. I would run both the "ePO:Duplicate Systems" and the "ePO: Inactive Agents" reports to see if you can clean up the System Tree any. If that doesn't yield any results, see if VirusScan is showing as a property of these machines at all, if not there may be something wrong with the VirusScan Plugin.
First take a look at the "last communication" time for these machines in EPO. This will tell you the last time the agent connected to the EPO server and updated its properties. If that is not recent then you have an agent-to-server communication issue.
If the agents are successfully communicating then review the following file:
C:\Documents and Settings\All Users\Application Data\McAfee\Common Framework\lastprops.xml
That file contains the complete property set that the client forwarded to EPO. Check and see if the VSE is reporting the DAT file correctly in that file. If it is not then the problem resides with the VSE install on that machine. The first step I'd take in that scenario is to apply the latest patch for whatever version of VSE is installed.
If the agent is communicating to the EPO server successfully and lastprops.xml contains the correct information then I'd recommend deleting the computer object out of the EPO system tree and allow it to re-populate and see if that clears it up.