I can't see how Firefox could be the culprit, it doesn't do any name resolution.
Your connection might be good so msn will work fine, it would be only new sites whose addresses are not cached that give you the problems.
have you had a look at whirlpool.net.au to see if others on TPG have DNS issues ?
I just had a quick look and found these:
http://forums.whirlpool.net.au/forum...?t=336541&p=-1
http://forums.whirlpool.net.au/forum...?t=336945&p=-1
TPG haveing a few performance issues, I think this is whats causing your DNS timeouts..