As a closure to the thread - I received a "daily account statement" from IB yesterday night, which shows the amount of check available. So they did receive the funds. The funds show up in account in TWS as well. HOWEVER, the funds status page under "account management" (IB website) still shows "notified" and "IB is awaiting receipt of funds". So it seems the data in funds status page in NOT very reliable. But - no more checks. I learnt my lesson.
DarthSidious, you need to check if your from TWS-->Account of your "buying power" got updated or not. IB's ACH-in is free and faster than the mail deposit. Even though IB's ACH-in is not as fast Ameritrade's (who makes the transfer it available to trade by overnight), it only takes 4-8 days;--but practically just 4 business days for the US customers). It would not even cost you the cashiers checks fee + postage and the fear of losing the check in mail. Unless you are sending a small amount, the wire transfer-in is the way to go at IB.