Google has either accidently or intentionally taken down your account. Possible reasons -
- You have multiple accounts (or you have logged into different accounts from the same PC)
- You have had problems with credit card billing before
- Somebody in this forum posted that after you reach certain number of impressions, Google "reviews" your account (not very sure about this though)
All I can say is wait for them reply back. If they don't, signup for a new account.
This time I set my campaign date WAY out in the future but next time I am sure I won't forget about it....