Right-click context menu scan window disappears during scan (v3.8.64739.471 x32)

When I right click and run a manual scan on a folder with 500 malware samples in it, the scan window disappears halfway through the scan. Another attempt will give me the message, “The scanner is busy with another task right now. Please wait until it is completed”, but I have to reboot to fix the problem.

Task manager shows cavscan.exe starts when I initiate the scan, then it disappears at the same time as the scan window, but I’m still unable to run another scan until I reboot.

AntiVirus set to any heuristic level or off
Firewall set to Custom Policy Mode and Highest alert settings
Defense+ set to Clean PC Mode

Athlon XP 2600 + 32 bit
Proxomitron and WeatherPulse running

I see someone else complaining of this in the wrong thread, so I’m gonna bump it.