From what you mentioned, it sounds like you have a duplicate GUID issue going on. This can hapen when the McAfee Agent is baked into the image and not properly sysprep.
You can either uninstall and reinstall the Agent on one of the systems or you can just delete the registry values. The below KB will walk you through removing the registry vaules.
Hope that helps
I already checked agent GUID in epo for the machines - but they are different. Maybe it would help to exlude the specific vendor MAC address - but I'm not sure if this has any side effects?
push ;-) no new ideas?
btw: it seams that only the "last" client disappears...
You mentioned VPN.
Are these computers connecting to your network via a VPN?
Also to double check. Are you running patch 2 for Agent 4.8?
There are a few bugs in there that might cause the issue (issues 14 &15)