From the way you describe it, it sounds as if your Firefox may be broken and needs to be re-installed.
First of all, what is "TopArcadeHits" and how did it interfere with Firefox in the first place ?
If the problems appeared after you tried manually removing all the Arcade files, try running a System Restore to a point before you made those changes. If things go back to normal, then try uninstalling that program more carefully. You could try a third-party uninstaller, such as the free version of Revo Uninstallner, or the iobit uninstaller, which comes with a "force uninstall" option.
Another place to ask these questions might be the mozillazine forums, with moderators and users who are experts in all things Mozilla:
Mozillazine Support Forums