Wordpress Admin - Insufficient Permissions

Run into a strange issue today. Was setting up a new blog using the cpanel worpress add-on and everything was fine until I tried to login as admin into the backed. Sure enough the details were accepted, but instead of the dashboard I was greeted with this message:

You do not have sufficient permissions to access this page error.

After a bit of searching it seemed it could be a corrupt db, so I reinstalled, but the same thing happened. Then I had a hunch, this was the first time I was trying to setup a custom table prefix. Sure enough changing the prefix back to just “wp” in the installation form fixed it.

WordPress: v3.2.1

Must be something messed up in the install script or somewhere refers to the default prefix where it should use the custom one.