Reasons for Firefox hanging

If you just install some extension and Firefox hangs upon loading, it could be due to some of the following reasons:

1. A file inside the extension package is misnamed. I once gave a XUL file an .RDF extension and Firefox just hung. No error message. It sat at around 14MB of memory and showed no CPU usage.
2. Something is wrong with the extension's install.rdf file or the content\contents.rdf file. Maybe the URI of the extension is not parsed properly (see another topic on that).
   

Well, what can you do? You can delete Firefox's profile on your machine (if you don't miss your usage data) by killing the Firefox subdirectory in:
C:\Documents and Settings\{your user id}\Application Data\Mozilla
if you're using Windows. Perhaps there's something more specific in that directory to kill, but I haven't investigated. Note that reinstalling Firefox doesn't help