My child was playing with my HTC tattoo and he was try too many unsuccessful unlock patterns. When I try to unlock my phone it was asked for Google account credentials. But whatever I have try to enter I got a message:
"too many pattern attempts" and "invalid username or password"
The only solution that left was to do a factory reset :,(
And finally I found solution:
Enter your google username (with @gmail.com) and "null" as a password