Virtual Pc7.02 On G5 Imac


I have been running a copy of virtual pc on my g5 imac in the office
in order to inter phase with our accounting pc which is operating on windows xp-pro. The problem that I am having is occurring several times a day of late, usually after working in vpc7 for a period of time, and shows up as blacked out or odd colored icons and text characters on the pc desktop followed by erratic behavior and loss of performance. I have tried rebooting both vpc and my mac with basically the same results, it will function for a bit and then re-occur. The thing that has me baffled is that it does not happen all the time, I have gone for days with no problems and then will suddenly encounter this behavior 3 times in an hour. Any suggestions as to what might be going on?

I have been using macs since the introduction of the mac plus
and currently have a dozen of them operation in our office, all running os10.4 with a single pc for the accounting department, and I spend more time trying to keep that one pc playing nicely with the rest of the network than I do on all of the other computers combined.