omg this happened to me last night! I lost my mind.
What happened was that I legally paid for a dev account but then decided that it wasn't for me, got a refund by apple but still had ios 5 beta 2 running. I should of been notified before losing almost everything on my phone, not smart by apple to do that to people who did actually pay.
You have Beta 2. It expired.
I have 3 devices on my dev account:
iPhone (mine) - beta 4
iPhone (wife's) - beta 2
iPad - beta 2
Last night, both my wife's iPhone and iPad deactivated.
Same. Beta 2 expired yesterday.