what was your password before, is it possible someone could have just guessed it?
the poker sites should offer secure one-time-use password systems to high rollers. I don't know exactly what they are called, but they generate a unique password every few seconds and displays it for you on a little key-chain sized thing. I don't think they are super-expensive.
ebay is offering this service to its customers for FIVE DOLLARS!!
http://news.com.com/PayPal+to+offer+...3-6149722.html