[ QUOTE ]
Check the FAQ here or search for 30" monitors in this forum for discussion of what a dual link DVI port looks like, I'm not sure if you can plug a dual into a single without having to push really, really hard so that may not be it.
Or just try the 30" in the other port on the video card.
[/ QUOTE ]
From the specs listed on ATI website.
# Flexible display support
* Dual integrated DVI transmitters (one dual-link + one single-link)
x1300 Specs
What that means is only one of the outputs is capable of driving the 30in at the native resolution. Check your manual or look at the pictures in the FAQ to make sure you are plugging the 30in cable into the right one.