I just bought an LG W3000H because of the listed 2560x1600 resolution, however, upon hooking it up, I see it only has a 1280x800 native resolution. The specs for the monitor doesn't mention a lower native resolution. Is this simply a marketing scheme, that they don't even list the native resolution, or is it possible that I'm not detecting the native resolution right?
From the page you linked there is a manual that shows the following:
It appears that your monitor has two default resolutions that it natively reports and I suspect that if your graphics card does not support the higher horizontal frequency that your monitor expects for its true native resolution and so is falling back to the other "native" resolution of the monitor.
Looking at your comment I would fully expect your graphics card to support that resolution, but I believe above 1900*1200 you require "Dual Link" DVI for it to work.
Next I would have a look at the cable you are connecting to your monitor, that resolution may require a cable that is "Dual Link DVI" compatible. I've found an image of what to expect from various cables but it may be that you simply need to buy a higher quality cable. If you have any other DVI cables you can try then I would start there.
Yep, Check the cable or get a new one (information from this page):
Looking at the product specs and manual for the LCD, the native resolution is 2560x1600 @ 60 Hz. And should support that resolution.
The problem might actually be your video card. It might not be capable of that resolution, or that resolution at that frequency. Check your video cards specifications.