Either you got a keylogger or your Pass, ID and SA is really easy to gues.
Dont use the your char name / forum name as your sro ID (you'd be suprised how often this is the case), use letters and numbers in your pw (change it every month or so), dont use a true answer on your SQ and most of all dont download stuff you dont trust. Decompile and/or scan non-official stuff you download. If you really want to be save use a virtual keyboard with hidden characters.
Its not very hard to hack an account since there are alot of people out there that use public information (if you know where to look) as their protection.
Anyway I hoped this helped and Goodluck