Try the Firefox Safe Mode to see how it works there. The Safe Mode is a troubleshooting mode, which disables most add-ons.
(If you're not using it, switch to the Default theme.)
You can open the Firefox 4.0+ Safe Mode by holding the Shift key when you use the Firefox desktop or Start menu shortcut.
Or use the Help menu item and click on the Restart with Add-ons Disabled... menu item while Firefox is running.
Don't select anything right now, just use "'Start in Safe Mode"To exit the Firefox Safe Mode, just close Firefox and wait a few seconds before using the Firefox shortcut (without the Shift key) to open it again.If it is good in the Firefox Safe Mode, your problem is probably caused by an extension, and you need to figure out which one.
I too have the problem that my Firefox windows won't move in Windows 7. But I have no time for screwing around with this posted diagnosis nonsense. Obviously your software doesn't work and you have no clue as to why and you want me to help you diagnose it. Well, the hell with that, I'm back to Windows Explorer. It works fine. This only confirms my thoughts on "free" stuff. We get what we pay for.