I posted recently on trying the Google Chrome browser after Google Reader and Google Mail suddenly slowed to a crawl in Firefox. It turned out that the latest Skype extension for Firefox was causing the problem. I had upgraded Skype to version 18.104.22.168 and elected to install the Skype extension for Firefox during the Skype upgrade. Others have also reported this problem recently.
So if you’re experiencing problems with Firefox suddenly being a lot slower than usual, particularly when viewing Google Reader, Google Mail and Facebook and you’ve recently upgraded Skype and installed the Skype extension for Firefox, uninstall it and things should improve. Doubtless Skype will fix this buggy extension in a later release. Thanks to Scotian who posted in the comments of the Chrome post and resolved this problem.