I have had a couple of UG files translated to VDA using SolidWorks but the key point is that you need to have a UG file exported in the native parasolid format. This may be your problem.
The VDA to KUM option is to import a curve into KUM as a nominal value for scanning.
If you wish you can send the file to me to try if there are no problems with that.
Tony Bryce
Sandia National Laboratories
Alb. NM
eabryce@sandia.gov