Access Forbidden Error

Hi,

I have a laptop running win XP home and IE 6 sp1. There is
a dialup account which works fine. And when connected one
can browse the internet without problems. Now I've added a
wireless card to connect to my wireless network, but still
have the dialup account to use when there is no wireless
connection.

When I'm connected to the wireless network and try to
browse the web using IE I get the strange
error: "Forbidden Access" etc. etc. as mentioned here:
http://support.microsoft.com/default.aspx?scid=kb;en-
us;316699

However, this kb article seems useless as my dialup
connection is not corrupt, because it works. It is only
with the wireless network that I have this problem!!

Please help ASAP if you can,

Thanks in advance