^^there are two Contextual Menu Items folders. Remember to look in your home folder too.
aaand if I was just a little bit more awake I would have noticed that you've already been looking around in your home folder. my bad.
edit. according to this webpage
http://www.mac-forums.com/forums/os-x-operating-system/150610-can-not-download-anything.html -- all you have to do is remove the plugins from the Internet Plug-ins folder in both the user and root Library and then restart your browser.
If that does not help then I'm stomped.
edit again.. I just took a look through the Resources folder of the Folx application and I noticed a thing called FolxIM.plugin. Try looking for that in your Macintosh HD/Library/Input Managers/ folder. I'm not entirely sure that this is what keeps the Folx plugin alive, but it looks just like it might be an Input Manager. After removing it you should logout in order for the system to get rid of it.