that is what i am trying to tell you - to find out if it is a hardware issue, put your os9 install disk into the drive, boot and just leave the computer in the graphical install (assuming here os9 install is graphical - like osx) if the screen appears to be wobbly there too you know it is a hardware issue!!
same with a linux live cd - boot, and leave the computer in X11 mode and wait for the 'wobble' effect to appear - if it does you have a hardware issue - if it does not - well - then i dont know what it is
please read this thread
have you actually googled any at all?