Pending file submission is hanging

The program is currently hanging when I try to submit a pending file. The green “submit” button remains in its depressed (or pushed) state, and I am unable to kill the process in Task Manager. I’m not sure if it hangs forever or for only a limited amount of time, as sometimes it becomes responsive again if, in the meantime, it “learns” new behaviors of other software.

I am currently using an Limited User account. A few days ago (when it last worked properly) I might have been using the Administrator account.

Windows XP Home, 2002, SP3
SpyBot Search & Destroy
avast! 4.8 Home Edition
AMD Sempron 3000+