Well, after importing probably a thousand meshes into UnrealEd, I've finally hit a brick wall.
For some reason, when importing this certain mesh, I can import it successfully, but for some reason it turns a 1.2 megabyte .ase file into a huge 56-70 megabyte .usx file, (when saved alone with no other meshes in the package). I have tried importing it as a .lwo with the same result. Polycount on the mesh is 2500 (while I have easily imported meshes with 6,000/10,000+ polygons without this problem), with a similar vertice count. However, I believe the issue lies in when it does its BSP collision tree. When importing it ranges anywhere from 20 seconds to a minute and a half of just working out the collision tree, where as in other models it does it nearly instantly.
I have tried both importing karma primitives, (MCDX) and not importing them, and it doesn't seem to significantly affect it either way. Was wondering if anyone else has come across this problem, or perhaps one of the devs know's where I am going wrong.