If you go to yahoo messenger on main yahoo page, there is a place to register
to be notified when the messenger for Vista is released. I also wrote to
messenger help and received the following:
Thank you for writing to Yahoo! Messenger.
We understand that you are unable to use voice chat or voice conference
through Yahoo! Messenger.
We are aware of an issue with Microsoft Windows Vista users not having
the ability to utilize the Voice Chat and Voice Conferencing features
through Yahoo! Messenger. Please note this does not affect PC to PC
calling or Yahoo! Premium Voice services through Yahoo! Messenger. Our
engineers are aware of the issue and are attempting to determine the
best course of action to resolve this issue.
We apologize for any inconveniences this has caused and appreciate your
patience while we work to resolve this issue.
We are very appreciative that you have taken the time to bring this to
our attention and would like to thank you for using Yahoo! Messenger.
Thank you again for contacting Yahoo! Messenger.
Regards,
Mary
Yahoo! Messenger Customer Care