Are there any other anti-virus/spyware programs running in the background that may be causing the issue?

Try this:
Start Menu -> Run -> type in "msconfig" -> choose selective start up -> browse the Services and Start Up tabs

Use this tool to select which programs you want to run automatically and which you don't.

It's going to be different for every system. Any programs relating to third party anti-virus/scanning/firewall software can be disabled. In general, I would leave Microsoft processes alone; those processes can be turned off somewhere in control panel if needed.

Not to hijack but I've seen the occurrence of random unknown errors go up since the recent pvp.net patch. Prior to that it was actually rare that I would see one.