hello, this is an error on the sever-side at the moment and not related to the version of the browser you're using - there's nothing you can do on your end to solve the problem. however the problem is already known and getting worked upon, hopefully it will get fixed soon...
Thanks for the tip MadPerson.
Clearing cache was first thing I tried.
Then tested using safe-mode to confirm problem.
However, have retested just now and all OK on XP box too.
All the best,
Still not working: when I go to https://www.mozilla.org/en-US/plugincheck/ it freezes my Firefox 18.0.2 and is giving a "This program is not responding anymore". Did try it also with Firefox in safe mode but same result: Firefox freezes. Also tried to clear the cache as suggested but same result: freezes. This on Windows 8 Pro 64bit.