I've had a problem where all the Windows server 2003 R2 VMs on at the time blue-screened with:
*** Hardware Malfunction
Call your hardware vendor for support
*** The system has halted ***
Interestingly the vCenter Applicance that was on the same box and running at the time seemed to be unaffected. The only thing I can attribute it to is exporting system logs from the client at around that time. The events tab for the VMs only shows the reset I did after it occured, there are no other events from around that time. Is this a known issue?