programs unload themselves?

[LB]

After a few hours of running a VBA program I noticed that it stopped
with some sort of a memory error. Next thing I noticed was that
whenever I double-clicked my dial-up ISP icon, nothing at all happened.
Next I noticed that a DOS based program I had would load and operate
normally, but after about 10 seconds it would unload itself for no
apparent reason. I noticed the same thing happening with the old
Windows 3.1 cardfile program. It also happened with Norton Anti Virus
2002. But it didn't happen with M.S. Word and Excel, or Quicken, or any
other program I tried. These behaviors continue until this day.

I suspected a virus, and installed Norton Anti Virus 2004, and SpyBot
Search and Destroy. These programs operate normally, and show no viruses.

I ran the exhaustive diagnostic software that came with my Dell
Dimension 8200. It showed no errors except when it was doing the hard
drive test, in which it showed errors that said they could have been
caused by write protection (though I doubt this was the case).

I suspected a RAM problem, and so ran the extended test of the aida32
program from Microsoft all night. It got up to pass 31, and showed no
problem, but their literature indicated that only a memory swap could
positively rule out memory.

Any ideas on what to do next? Thanks for any help.

 

[LB]

Resolved the problem. A virus evidently was keeping Norton from
functioning properly so I couldn't detect the virus. I ended up
visiting the Symantec web site and doing a virus check on-line. It
found the W32.HLLW.Gaobot.Gen virus in a single executable file in
windows\system32. When I eliminated it the program unloading problem
immediately ceased and all things have been restored as before.