I would go to C:\Program Files and delete the Mozilla/Firefox folder then download a fresh copy of Firefox and install it. All of your bookmarks, settings, and extensions are stored separately and will remain intact, so this will simply address the corrupted file(s).
Hope this helps,
I have been running Firefox for several months with no problems on this win98SE, but suddenly the program will not load. The error msg is ?FIREFOX caused an invalid page fault in module JAR50.DLL at 0167:6001134d.? This dll is part of the Firefox program.
I decided to remove Firefox and reinstall, but I cannot remove the program from Add/delete in control panel or by using the uninstall file in Firefox. Tried Ad/Remove Pro also with no luck.
I have run out of ideas---can anyone help?