Hi,when you split aces, you can't hit/double on the new cards. it's not a bug, it's intended (as the "No Hitting Split Aces" fairly commonly used on blackjack tables). But it's not written in the "How to play" rules, I might add that :)
But splitting a pair of tens and getting a 21 should not prevent you from playing the other hand.
PS: Getting a 21 after splitting a hand is not considered a Blackjack. So if the dealer has Blackjack and you have a split 21, you will lose the hand.