Found this on the Prevx forum:
Search Prevx forum for "mismatch"
You will find answers like (and i quote Prevxhelp):
{QUOTE-> This false positive is caused because of a mismatch between usermode data and kernel mode data and is detected within our rootkit scanner. I suspect most other antirootkit programs would detect this as well and it literally means that the file has a missing entry within the file system (which is a technique used by some advanced rootkits today).
However, the cause of it generating a false positive is very rare and usually would only happen either from harddisk corruption, another AV blocking that specific file (which I doubt in this case), or a file having just been written to the disk/created.
<-QUOTE}