Yup had it happen to me. How many times did you withdraw money from them? <== do not have to give answer , but I did!
I phoned the site and got one on one with one of their reps. After feeling it was the real thing I did give the requested info to said person and still have a record of that stored else where as to have in case my info get used in other ways.
So investigate first, set terms for transfer (get as much info from them as to whom you are going to deal with, use excuse you are doing that so transaction will proceed quickly, but keep all gathered info and store in a second place and not just on or in your computer.
If their query is real it will be OK, but if not you got record to go to fraud squad may it be federal, state etc. law enforcement.
That's what I did. Good luck and cover your butt.