Best guess? You might have a corrupt file in your Yahoo! Messenger directory. To fix the problem, you must manually delete the Messenger directory on your C: drive (default), then reinstall the Yahoo! Messenger application.

[Note that deleting this directory will also delete any archived messages on your computer. If you want to keep them, first move your profile directory out of the Messenger directory:

• Close Yahoo! Messenger (if it is currently running).
• Go to your Desktop and double-click "My Computer."
• Select the "C:" drive.
• Go to: C:\Program Files\Yahoo!\Messenger\Profiles

Your folder will be named with your Yahoo! ID. It contains your complete Message Archive. Copy it to another location on your computer before deleting the Messenger directory. You can then move it back after re-installing Messenger.]

To delete the Messenger directory:

1. Close the Yahoo! Messenger application if you currently have it running. Make sure all instances of Internet Explorer are closed.
2. Go to your desktop and double-click "My Computer."
3. Click the "C:" drive.
4. Go to:
   C:\Program Files\Yahoo!
5. Highlight the Yahoo! Messenger folder and press the Delete key on your keyboard. (All archives will be deleted if they are not copied. Please see below.)

To install:

1. Close all running applications except for your Internet browser.
2. Visit the Yahoo! Messenger home page.
3. Click the "Download Now" button.