I don't want to sound like I'm getting above you, Katahu, but there is a much easier way to take care of colocated vertices than deleting the object.
I used to get frustrated when I would get that error message, and stop working on the project altogether, but someone told me about a nifty little gadget in the modifer section called "weld". I had never noticed it before, but it seems to be created for just this problem. To use it, select the object, go into sub-obj modification and select all the vertices. Now scroll down the modifier command bar, and pay close attention. About half-way down you should see a section called "weld" with a couple of buttons that read "selected" and "target" below it.
With all the vertices in the object selected, click "target" and change the number next to it to 1. I'm not exactly sure what this does, but it has something to do with pixels, and if you want the object to stay the same shape, the smaller the pixel number the better.
Now highlight the number just above the pixel number. This is the amount of space that can be aloud between vertices when you press the "selected" button. If the vertices are closer than this number indicates, they'll be colapsed together. Make this a small number. I usually use something like 0.125", but you can use whatever you like.
Now press the "selected" button. Continue pressing it until you get a message saying "no vertices within weld threshold". There you go! Everything should export now!
BUT
I don't think this is the problem with Moach's stuff. It says this:
Start! (C:\gmax\gamepacks\FlightSim\ximango)
Loading X C:\gmax\gamepacks\FlightSim\ximango...
Error in exporter: Mismatch between # vertex faces (500000) and # normal faces (943835) in part Bone01.
Error!
Error!
And I don't know what that means.