Usually this means you have a cached browser cookie, that's out of sync with your server side.
Quick test, access phpMyAdmin with another browser. If error clears, then simply clear cookies in your other browser.
If problem persists, this is likely a server side issue. Permissions or phpMyAdmin config has been scrambled somehow.
If it's a server side issue, this is easy to fix using root ssh + near impossible trying to use non-root GUI interface.
Best to contact GoDaddy support via chat, if this is the case.
