Open up your Home Folder by clicking Places>Home Folder
Press CTRL-H (or click View>Show Hidden Files)
Find a folder called .gnome2 (it has a period at the beginning of the name) and open it by double clicking on it
Inside of the .gnome2 folder, there is another folder called keyrings. Open it up.
Delete any files you find within the keyrings folder
Restart the computer