If so it may be removing cookies quickly for the site.
Next delete your browser cache.
In Internet Explorer click on Tools > Delete Browsing History (In IE8, this will be under the Safety menu instead). Make sure cookies and Temporary Internet Files (if using IE8, uncheck preserve favorites if CHU is in your favorites).
In Firefox, click on tools > clear private data. Make sure Cache, Cookies, and Offline Site Data is checked and click OK.
Afterwards, restart your browser and attempt to log in again.