I would start by disabling all add-ons. If that solves it, enable them one at a time until you find the one that causes it.
If that doesn't work, something in your configuration may be corrupted. Reinstalling won't necessarily solve this. You may have to uninstall FF, then delete ~/.mozilla/firefox/xyz.default (where xyz can be anything). Then reinstall FF.
Unfortunately that will lose all your add-ons, configuration and bookmarks (unless you have Foxmarks installed, in which case you can reimport them).
Before you criticise someone, walk a mile in their shoes. Then, when you do criticise them, you're a mile away and have their shoes.