SampleTank and Midi Files

I have gotten SampleTank 32bit to work on Sonar Artist thanks to help I received from this forum.  Now I am seeing something that I don't quite get.  If I open a midi file in Sonar it defaults to using the Cakewalk TTS soft synth.  I then used "replace synth" to change it to Sampletank then I start loading sounds for the different tracks and did a save as to indicate it was a working file since I haven't finished picking all the instruments for each track.  When I reopen the saved file the SampleTank track that all the midi feeds to is converted to a midi track and Sonar adds another audio track with Cakewalk TTS and I essentially lose all the SampleTank settings and all the tracks are now connected to Cakewalk TTS.  Any idea what would be causing this? 

I think you are correct.....I double clicked the midi file to open it in Cakewalk and then when I was ready to save I did a save as and changed the name and I don't think it prompted me for the file type.....so I am sure it save it as a midi file without any of the changes I made.   What I did last time was open a default template and imported the midi file then made my changes and it saved as a Cakewalk .cwp file and that seemed to work.  I am guessing if I had just made sure to save it as a .cwp then it would have worked the way I originally did it.  Thanks for the help.