Get a USB , save all your important files. Delete your Standard window account that you play runescape with and make a new one. CHANGE ALL YOUR passwords again.
That's what happend to me when I constantly got hacked and I did this and it worked.
If you use an on-screen keyboard, he won't get your password as the keylogger only gets typed information, that's why fagex was smart enough to put a bank pin that needs to be clickable and not typed.