Problem with Firefox for IS X

Hi,
For the last two days whenever I am attempting to use Firefox for IS X, I have been shown an error message which says,
"The page you are trying to view cannot be shown because it uses an invalid or unsupported form of compression".
Nevertheless, I successfully downloaded many things from the net. It often happens while visiting any web page including the most known ones like google, YouTube, Facebook and so on. Once or twice refreshing the pages worked well. I am here to seek a solution.
I have been using Mac OS X Lion.
I have already tried un-installation and installation of Firefox. But it didn’t work.
Can you tell me what to do now?
