I haven't changed the MPCORB database... that's a product of the Minor Planet Center. And the making of the mdb file just uses the same orbital elements as are in the text file from MPC.

The MPCORB component was changed 30-Sep-09 for 32-and 64-bit compatibility. It simply supplies orbital elements to AcquireSupport.CalcEphemeris(). That, in turn, uses the Kepler and NOVAS components to get the final J2000 coordinates. Both Kepler and NOVAS are now the responsibility of the ASCOM platform development team, specifically Peter Simpson. If you installed ASCOM 5.5 I think you have the latest ones. I don't believe he changed anything in the algorithms or the object model, he just made them more friendly to .NET, Win7/Vista, 64 bit, etc.

I just got in from NM, so I'm not in a position to construct a test harness, contact Peter regarding possible changes, etc. If you want, I'll lend a hand next week though.