you are using Firefox?? or is it SeaMonkey or Konqueror
so you did find the tutorial about setting firefox in" about
:config"to turn off ip6
and you are using " OpenDNS "
how much ram is there on the computer 512 or 256 or do you have a good amount 1 to 4 gig of ram
The problem occurred a few days ago, I think after an update.
the last ( fedora 9) update had some SELinux updates
off hand i would guess , like you probably have, that it is something to do with the router