johnus_350 - what firewall are you using? Configuring it properly may be all that's needed.
Yahool Voice chat uses TCP ports 5000 and 5001 and UDP 5000 to 5010. You need to open those ports through the firewall.
(Note: If you're trying to use voice chat at work through their network, it may be the ports it uses are blocked and there's no way around that. No way without jeopardizing your job, that is.
)
If you are also using a router, you will need to either forward those ports through the router or put your computer in the router's DMZ, which effectively bypasses the router's firewalling abilities.
The information linked to on
this Yahoo voice chat page might give you the solution, too.