Firefox only connects after a ping

I wonder if any of you kind people could please solve a little mystery for me?

Having finally got Debian Sarge installed to my near satisfaction (what a trauma that was!) I'm now able to connect to whatever website I feel like from Konqueror. Firefox, however, simply times out after a while, as does apt-get and tin.

I've found out that if I ping the domain-name in question from a bash shell and THEN connect to it with firefox, it does connect. Same with apt-get and tin.

So, my mystery is a) why doesn't konqueror need the ping to make it work? b) What do I need to twiddle to enable firefox-apt-get-tin to connect without doing a ping.

I'm just about savvy enough to guess that this is "something to do with DNS", but beyond that I'm in the dark. I'd be very grateful for some illumination.

Details: I'm running Debian Sarge 3.1 on a Dell Inspiron 8100 laptop, The kernel is 2.6.8 to accommodate the ndiswrapper modules shipped with Debian which only seem to be for that kernel. I'm using the versions of ndiswrapper and wpasupplicant that ship with Debian Sarge 3.1. Security settings-software firewalls-etc are whatever you get when you install Debian, i.e. I've done nothing further to the set-up in that regard. I'm connecting wirelessly through a D-Link DWL-G650+ PCMCIA card to a D-Link DSL-G604T router-modem.

Cheers, -- Rick