2400MP not synching with laptop

I project DVD (opera) clips from a laptop.  I used a Dell Inspiron for a while, have recently switched to MacBook Pro.  Initially the projector worked with the MBP, but last time out, from the outset it wouldn't pick up the signal from the laptop with either VGA or S-video cables.  And whereas the screen would normally bring up a blue background, now it stayed white with "searching for signal."   Any experience or clues?  Is the 2400MP a mismatch with the MBP?