Avast Anti-Theft SMS UNLOCK does not work

Hello everyone.
This is my problem: after removing my SIM from my ASUS Transformer Pad TF300TG (and put the same SIM again in it) I have no access to my tablet because everything I try to unlock it does not work! It receives UNLOCK sms from the “friend” number but they do not unlock anything at all. This tablet is not listed in my avast account so I can’t try to unlock it from my PC.
Any suggestion!!!?

http://www.avast.com/faq.php?article=AVKB135#artTitle (Changing a SIM card)