Hello,
I guess that your problem is related to bugs in the Firefox packages of your distro and are not TDE related. Except being horribly slow on older computers (such as P3 and P4), Firefox should be stable. This is why I will replace it with Google Chrome (or Chromium) on my next livecd. You can always test if your connection is good by trying to use Konqueror.
Merry Christmas!
-Alexandre