I tried to load the FFX DC-9 in FS2004 and after I set the fuel I clicked ok and FS2004 crashed. What do I have to do to get this plane working in FS2004?

No one knows?

Nope. But if you like flying DC9, maybe you should make a big hole in your wallet and go for the Flight1 DC9. I have a bunch of payware ac's but this one is my #1 commercial (has a nice old SAS livery too). And beeing this old there's no boring FMC preflight and you get busy navigating up there. And the startup from dark and cold is fun too, seeng all those light go out one by one ... and there's a lot of eye candy:http://forums.avsim.net/user_files/53396.jpgEagle

I had the same problem except with the FFX-727 I discovered that the plane loadout was heavy. What I did was edit the aircraft.cfg .I removed about half the weight from all the stations and I was able to finally adjust the fuel with no problems. Try this and see if it works for you .I dont know why this worked this was but it did .