Try this
http://forums.mozillazine.org/viewtopic.php?t=288184
Looks to have solved others issues and lots of interesting stuff to play with!! Try changing the "browser.enable_automatic_image_resizing" value in
about:config, might be what you need.
I have also had problems which forced me to create a new profile in FF "firefox.exe -profilemanager" This did sort out the problem (settings lost on every start)
I've also had FF freeze a few times when having multiple tabs open (10+), which may be due to having that many tabs open, but should not be an issue and it was always fine in previous versions.
Nothing to force me back to IE, but nevertheless I think there are some issues with this release that are hopefully rectified soon.