New version of vBulletin was updated this morning.
Clear cache/cookies/temp internet files/history
Reboot and you should be good to go.
I just cleared the droidfourms.net cookies from my Firefox browser and logged back in again. Worked for me.
For anyone else, in Firefox select Edit/Preferences/Privacy and click on "remove individual cookies". In the search field, type in "droidforums.net". It will list all of the cookies associated with the web site. Click on "remove cookie" for each of the droidfoum.net cookies in the list.
Once I did that, I was able to log in just fine.