Web sites prompting for Network Passwords

Hi,

First post here so please dont flame me too much! Ive done a search and cant find my problem so here is my question:

Over the last few days when browsing the net, I am constantly getting the 'Enter Network password' dialog box coming up.

For example when I go to www.multimap.com I get a dialog box with site name www.dgm2.com asking for username and password, If I go to www.sky.com I get a login box for oad.realmedia.com.

The only way to continue with this is to cancel the password box several times which is very frustrating. Im sure it's something simple, so can anyone point me in the right direction?

BTW, Im running W2k SP2 and IE6.

Cheers

Mark