LazyLion
King of de Jungle
I've come across this problem now on a few different installations of Ubuntu with Firefox. When I go to right click on a link (usually to open in a new tab), most of the time the right click context menu does not appear, but a random action takes place based on the right click menu, as if it opened and got clicked at random. It is very frustrating... so much so that I can't use Firefox. 
I am going to try a different browser for a while and see if it does it... meanwhile you can read more about it here....
http://ubuntuforums.org/showthread.php?t=741228
http://ge.ubuntuforums.com/showthread.php?p=5449547
http://ubuntuforums.org/showthread.php?t=718522
https://bugs.launchpad.net/ubuntu/+source/mozilla-firefox/+bug/148381
I am going to try a different browser for a while and see if it does it... meanwhile you can read more about it here....
http://ubuntuforums.org/showthread.php?t=741228
http://ge.ubuntuforums.com/showthread.php?p=5449547
http://ubuntuforums.org/showthread.php?t=718522
https://bugs.launchpad.net/ubuntu/+source/mozilla-firefox/+bug/148381