Virus in iOS5?
p.twimg.com
This dialog popped up with the phone in a standby/locked state. Both the lock and the home button would not dismiss it. The dismiss button pictured did remove it, however.
iOS5 was installed from the official developer build, downloaded from a valid iPhone developer account.
Apps running: phone, safari, photos, contacts, messages, mail, settings. This dialog appeared from the phone being locked. It could not be dismissed by either the home or lock button. The dismiss button shown, removed it, however. The only apps running at the time were built in iPhone apps, such as safari, photos and mail. I believe that's just a Class 0 SMS.