just export ascii instead Math89, you can always convert it to DBO later.
Zeerun: It can be a pain in the arse to get working.
I'm guessing you have used the skin modifier.
you need to select all objects, then go to export selected. All the objects must be connected somehow on the heirarchy.
you want to export normals, tangents, skinning, bones, material and on animation you need to create just 1 animation set, from the beginning to the end of all the animation. the .x format allows for named animations within the file, but DBP doesn't, so you have to save it all as one.
I can't really be more helpful, as I'm at work at the moment, so I can't just take a screenshot of my settings. You can either wait until i get home so i can post my settings properly and have another crack at it, or either upload the model here or email it to me, and i'll have a crack at exporting it and let you know what i had to do to make it work.
Manic
I don't have a sig, live with it.