I have this problem too, then when I try to instal another program, it tells me firefox is running and I need to close it. But the window isn't there, it never shows the tasks list when I ctrl+alt+del. So if it is running, nothing visibly shows that it is. Very frustrating cuz I love firefox.

This is a bigger problem than seems to be realized. I also have it. Were you able to run the install wizard without that "another copy running" message? I have not been able to do so, and as a result cannot uninstall Firefox to try a clean reinstall -- since the uniinstall wizard generates the same message. thinks another copy is running. The profile.ini program seems to be exactly like the example show of a proper profile file, so that can't be it either. And the colunteer help desk was not staffed Thursday PM or Friday to see if some hand-holding might resolve it.