Avast has blocked my Nokia C7?

Immediately after install Avast, the Nokia C7 ask to me “Block now?” I say Yes (error) and now the phone want a Mobile Security Code Which I had never set!

Afet I put off, I put on again, it asked pin code (its OK9 then the code to unblock the phone (ok again) and then it ask a Mobile Security Code… ???

Please someone can help me? I cant use my new phone… Thank you very much