Download and Install MalwareBytes Anti-Malware, run a full Scan. http://www.malwarebytes.org/. This helps check that there are no viruses on your computer causing issues. You can uninstall this program after you clean off any infections.
After doing these steps, go ahead and update to Firefox 14.0.1.
Here is a recent post by a Firefox user with a similar problem in the Bleeping Computer forums (do NOT follow those instructions, which are specific to that user. It's just an example of type of help you can get there):