It sounds to be as though you've not installed the GMax version of the Gamepack, but instead tried using the Max version!

You need to copy/paste the FSX_GmaxGamePack folder from the SDK to your GMax folder:

C:gmaxgamepacksFSX_GmaxGamePack

In fact, there was no need whatsoever to reinstall GMax or get rid of the FS2002 and/or FS2004 gamepacks!  ACES (MS Game Studio) set this up so that you can keep your current installation and simply add the new, FSX gamepack!

Directory of C:gmaxgamepacks

02/09/2008  12:52 PM    <DIR>          fs2002
05/15/2008  12:25 PM    <DIR>          fs2004
07/23/2007  08:35 PM    <DIR>          fs2004_scenery
02/10/2008  05:20 PM    <DIR>          FSX_GmaxGamePack

As you can see, I still have four gamepack versions installed. I need only select which version I want to use by launching GMax from one of four Desktop Icons... ;)

I also recommend strongly that you join the FS-Developer Network forums, where you'll find the most up-to-date information on all things Flight Sim related.  Just look at the name of this forum to see how far out-of-touch it is here: "FS2002????"

http://fsdeveloper.com

also

http://www.freeflightdesign.com/