Not by personally having debugged - out of my league and toolkit.
But different sets of drivers showed different kind of symptoms -
which were not visible on other machines running the same OS and VM system.

As they deinstalled and reinstalled a few times this was the clearly changing difference.
While no proof the driver to be at fault, this smells more from that area.

>Can you specifically point to the Dell drivers/hardware as the problem and not the VM software?
>
>>The company I work for often had pure Dell turn of the century and they were telling it everybody.
>>Now about 1/3, and one machine is giving trouble with the USB port in some VM setups and driver versions.