Wireless network problems with Yahoo! properties

I have a really weird problem with my wireless network - it is a
Microsoft Broadband Network Wireless network.

Intermittently, I seem to lose all access to Yahoo! properties - not to
any other websites, just Yahoo! ones! mail.yahoo.com and www.yahoo.com
are particularly frequent losses, but sometimes also my.yahoo.com and
others.

I checked with my ISP and it seems it is not their issue, as when I
remove the wireless network all is fine, but when I reinstate the
wireless network these sites are often not accessible. tracert and
nslookup results are bizarre at these times.

tracert immediately gives back the message "unable to resolve target
system mail.yahoo.com" - it doesnt even attempt any hops!!

Yet for all other sites except www.yahoo.com and mail.yahoo.com tracert
works fine.

nslookup comes back with the message Cant find server name for address
192.168.2.1 : Non existent domain

192.168.2.1 is my router's address I believe
Can anyone help?
I am baffled!

Michelle