LCD monitors aren't like CRT Monitors. LCD monitors have a ''Native'' resolution that must be used to display properly. Check your manual and set your graphics card's resolution to match your LCD. CRT monitors can display an infinite number of resolutions.
DVI output is digital only and goes directly to your LCD. VGA has to convert to analogue to drive a CRT monitor and early LCD's. No conversion means faster response times.
EMI is not an issue unless you have a very high power magnetic field very close to your LCD.
A final thought, have you set your BIOS to the correct Video device? You must disable the onboard video first. If not, your PC may be trying to drive both video cards.
You also didn't mention if you installed the new card's drivers, but I assume you did that. Does your LCD also come with drivers? If not sure, check the respective web sites for current drivers.
Hope this helps,
I just bought an LCD monitor to replace my CRT and a video card to replace my integrated video. Everything works great, with two major exceptions. First, on the left side of the screen, near the corners, sometimes the images starts to very slightly bounce or flicker (it really looks like the image stays still but the pixel colors are moving around). This only happens when I use the DVI connection, not the VGA, and its sporadic. The second problem is that the CPU usage goes to 100% after coming out of standby and there are redraw problems (I have to reboot). I've tried the latest drivers. Any thoughts? I was thinking that maybe the LCD problem was EMI but I'm just not sure.