I had this few times and found in another forum that another guy had the same.
Screen stops rotating. When I doublpress Home - rotation icon is unlocked. I try to lock it and unlock - doesn't help. When I restart the iPad (turn off + turn on; not just sleep/standby) - rotation restores and works perfectly. The other guy reported the same. Only device restart helped.
Both iPad2s are 3G (one 32GB and another 64GB model) with iOS 4.3.3 and both are jailbroken with jailbreakme.com.
Could that be JB related? Anybody have the same with or w/o the JB?