Radeon x850xt in an optiplex gx270

Hi,

I've been using a Radeon 9800pro card in my dell optiplex gx270 (the full size model, not the sff) for several years and it quit on me. I got a radeon x850xt card to replace it, but my system has no display with the new card installed. the machine goes through the boot cycle (from the sound of it), and the lights on the back indicate a normal boot, but i see nothing on the monitor  

I went and bought a new motherboard but have the same result. i've tried both the DVI and VGA connectors on the card and 2 different monitors. i have an old geforce4 mx440 card and if i put it in, it works just fine. the onboard video also works fine.

I sent the new card back, thinking it was bad. they sent a replacement and it doesn't work either.

So, is it possible that i've gotten 2 bad cards in a row or am i missing something? the install is pretty straight-forward (i.e. plug and play) but i'm about to go nuts.

Any ideas?


Thanks very much.