You can always wipe out your current keyrings by removing the file ~/.gnome2/login.keyring, but you should try resetting the password with the 'seahorse' program. Reinstalling gnome would do nothing, since it's all in your homedir.
This was part of an exchange in the fedora forums, and was easily overlooked as it was part of a larger issue that was, thankfully, solved.
Another part of this exchange was the following information regarding autologin, and how to disable it.
It sounds like you have auto-login enabled. Not sure how you managed that (is this a LiveCD?), but you can disable that by editing /etc/gdm/custom.conf and removing the lines between the [daemon] line and the [security] line.
I hope this helps someone else as much as it has helped me. :-)
The first fix regarding gnome keyring was the issue I experienced, and the second part regarding autologin was something that caught my eye as being useful in the future
Bye for now.
Have fun everyone!