Access to some websites & mail halts/disabled over wireless connec

Just installed a Netgear WG111 USB wireless dongle on my PC and had a rather
disturbing and persistent issue after install. It seems that now at about 5
minutes into the connection, I cannot access some websites or my mail
(sourced through a xxxxx.mail.com server). The wierd thing is that i CAN
still get to some websites, most notably those ending in.net or .net.au (eg:
www.abc.net.au) I can also contiinue to use msn messenger and Skype.

This happens each time I reboot - ie: it works for around 5 mins, then it
deny's access to most sites and mail. Just returns an error page or error in
mail app.

I have tried fiddling with Internet Protocol (TCP/IP) properties and
obtaining IP and DNS addresses automatically and manually (with ISP's
settings) but no good.

I have a sneaking suspicion the fault may lie deep in registry in the
'wireless connection' settings. Then again, I'm not really sure. Any help or
thoughts would b much appreciated. I really don't want to rebuild.