[Help] Collision mesh not exporting properly

Hello. I've been trying to troubleshoot why my collision mesh won't export properly. None of the forum post and tutorials I've read/watched have revealed what I'm doing wrong.

Here's my mesh in Maya:



And here's it with the collision mesh:



I've set all the pivot points to 0 0 0 and made sure that the geometry is sealed.

But still this is what appears when I import the .fbx into UDK:



The collision mesh seems to have turned into a thin, infinite pole.

I have used the UCX_*name_here* and named them UCX_Sign_1, UCX_Sign_2 and UCX_Sign_3. But when I import the model, only one 'primitive' is listed. I tried to use the MCDCX_ extension in another attempt, but the results stayed the same. I also tried using the .fbx exporter in 3ds Max, same problem.

Do any of you know how to fix this? It's been driving me nuts for days and I cannot find any solutions. Is there something I have to do with the geometry, or is the exporter broken?

Thanks for your time!