Well what you can try is manually deleting your cookies.
For firefox.
Goto:
Tools>Options.
Select the privacy tab
Select the remove indivual cookies link.
scroll to your site and delete all the cookies for your site.
Then login and see what you get.
For IE you will have a cookies folder but in windows it is hidden by default so you will need to change folder settings to view hidden files/folders to find them and delete them.
The only thing they might have in common is your internet security settings on your desktop is not allowing the cookies to update/add or delete.
