Just installed ATI Radeon 9800 Pro

I just installed a ATI Radeon 9800 Pro video card on my G4 MDD with 867MHz dual processor. When I turned on my mac for the first time it went to the grey apple screen just fine but then it went to a sky blue screen and none of my apps or my desktop loaded up. When I put in the old GeForce 4MX card that came with it back in it works fine. I reset the PRAM and NVRAM, but still it does the same as I have described above. I really need to get this mac working with the Radeon 9800 card so I can start editing. I'm actually using a dell LCD monitor with the mac so I'm wondering would that have anything to do with it? Does anyone have any suggestions or solutions to this problem?? I'd appreciate any help I can get before I decide to send the card back to the person that sold it to me.

Is the Radeon 9800 the "Macintosh" version...or the PC version that was "flashed"?

Is the video card new or used?

- Nick