Hi LHong, thank you very much for the reply, this is very encouraging news. To answer the questions, I now have Sonar X3 patched to the latest code, not Producer or Studio, running on Windows 7 (also all patched up).
Second these are all .WRK files I have created over the years but mostly with CakeWalk Pro Audio 9. Finally, these are straight MIDI files with no Audio tracks, or 3rd party plug-ins. I've even stripped out all SYSEX data as well, just simple automation exists like patch / bank changes, notes on/off, volume, panning, expression, temp changes, etc.
I've tested the process by opening up one of these WRK files in my copy of Sonar X3 and immediately doing a "Save As" midi type 1 file format and it works just fine, no problems at all with the resulting file.