From http://news.com.com/2100-1032_3-6099532.html:
Yahoo announced on Thursday the general availability of its latest chat application, which enables users to do a lot more than just chat.
The new Yahoo Instant Messenger with Voice, which offers telephony functions, features more than 180 plug-ins created by developers from inside and outside Yahoo.
Sorry to report that not is at all well with the Messenger 8.0.
Messenger 8.0 will not log me in at all even though I am logged in
to Yahoo Mail.
I also had similar problems with the earlier version 7.0 Messenger.
No problems at all logging in or using Messenger 6.0.
I wish I could go back to Messenger 6.0 which had no problems at all for me.
I am having problems with that Yahoo 8.0 messenger too! I can log fine into it, but every now and then, it just logs out, then back in by itself! I want to go back to an older version too, but not sure how, when I always get redirected to the 8.0. It messes me up when I am in a voice room too, and sometimes I cannot see other people’s text but my own. It does this intermittenly! Please help before I go crazy,lol!