projector problems connecting to DVI

Ok just bought myself a lovely optoma dv-10 all in one projector dvd player and sound system which is an incredible piece of kit for viewing DVD's, however the DVI to VGA converter messes up the signal on my 1.67ghz powerbook although i get a window telling me the powerbook can see the projector and i can go into mirror or side by side view but it doesn't display anything, I have tried vga from g4 tower that works, hooked up a g3 pismo powerbook & that works too. So it has to be a problem with the DVI to VGA conversion process.
Spoke to optoma aparently the powerbook and the projector are not compatible. (shucks) I have also tried s video connection and that only sends a b/w signal (strange) havent tried composite yet, but i'm wondering would a pcmcia VGA card work? Or can anyone suggest anything else that i haven't thought of

many thanks for looking