Another alternative

1. Un-install Messenger. The un-install is important; it removes any corrupt files that an install alone might not.

2. Click the “Start” button, click “Control Panel”, and open “Add/Remove Programs”. Scroll down to “Yahoo! Messenger” and remove it. (If you can’t find it, look for “SBC Yahoo!” or any item in the list with the word “Yahoo!” in it.)

3. Do a Search for any files beginning with “Yahoo” (i.e. search for Yahoo*). Search by clicking “Start”, then click “Search”. Delete all of the files you find.

4. Re-boot your machine to clear any files in the cache.

5. Install a fresh copy of the most recent version (Version 8 is available now – do not install the Beta version).

Note: By doing this you will lose any history of conversations but your contacts will still be there (they’re held on the Yahoo Server).

6. Re-boot your machine and you should be all sorted out.

Thanks, vangardx