If you Google "Dr Watson Postmortem Debugger has encountered a problem" minus the "" of course you get lots of hits. This is more of a Windows issue than McAfee's.
Sounds like the Windows installation is a little ragged. The best thing you can do besides re-formatting is by inserting your windows disk into the CD-ROM, go to Start/Run and type in "sfc /scannow", windows will look for damaged files and possible solve the problem altogether. Keep in mind the virus removal is VERY different from damage control, just because the virus is no longer present, doesn't mean the computer is fully operational. Viruses write irresversable code to the registry. This is the main source of frustration with viruses. If all else fails, format, there i said the "F" word.
Also, if you decide to format, be sure to back up everything your gonna want after, formatting is a final process.
Best of luck