I have just searched these forums, and our help desk. There does not seem to be "one" solution for this problem, and we have never been able to replicate the problem in the lab. Here are a few.
1. June 05. Support Ticket.
Symptoms: Upgraded from version 4 to 6, Could not access Yahoo "Read mail"
**** His solution: Upgrade from 2000 to XP ( ??? )
2. Nov 03
http://forums.qbik.com/viewtopic.php?t= ... yahoo+mail
Symptoms: LAN cannot connect to Yahoo Mail
***** Unconfirmed solution: When using Yahoo Messenger, use SOCKS proxy. He had to tweak his satellite connection for Yahoo Mail ( ??? )
3. Nov 04
http://forums.qbik.com/viewtopic.php?t= ... yahoo+mail
Symtoms: Cannot open Yahoo mail.
**** Solutions. Have a read
Extra ideas:
1. Turn off the cache in WinGate and test.
2. Does this problem still happen when only using NAT (No intercepts / proxies)?