
You may have been emailed this, but the IIsi's power supply is not rated to
handle the GC board.  Remember when the si came out and everyone complained
about it's power supply.  This is one result of apple providing a low-cost
computer and I think they got a lot of flack for having a relatively high end
computer (at the time anyways) that couldn't even support their own video
board.  Even if this isn't what is causing your problems, you might develop
one later.