Jeremy Zawodny has the scoop on the Yahoo Messenger for Linux:
It’s unofficial and unsupported. Use at your own risk. It’s version 0.99.21. It’s here. It fixes some very annoying bugs that users of 0.99.19 are likely seeing.
If you’d rather wait for the next official one (rumored to be 0.99.22) hang on a week or two. It’ll probably appear on im.yahoo.com.