I have a midifile I'd like to use. When I click the midifile to listen, it opens in Platinum and there are tempo changes throughout the song. I close Platinum, and then re-open to create a new project. I import the same midifile and now the tempo is defaulting to 120bpm from start to finish. Any suggestion on how to import the midifile as is without it defaulting to 120bpm tempo? If not, then how can I edit tempo changes manually at certain measures?

See:  (This is for X2 but is applicable for platinum)

http://www.cakewalk.com/Documentation?product=SONAR%20X2&language=4&help=Recording.37.html
 

If the file has the tempo variations you already want, you can open it (like you initially mentioned) which will route the TTS-1 for you (no MIDI output assigned in SONAR preferences). IIRC, you need to add a "Master" buss after that point, but you can "save as" and change it to a cwp file. After that, if replacing sounds, you can insert VSTs and shift-drag MIDI clips from the TTS-1 to its replacement (ctrl-shift-drag for reinforcement/layering).
 
As far as the tempo map itself, you can open that view to edit existing ones, or add tempo changes as well.

Yes, opening a MIDI file as a new project preserves the tempo changes, and importing drops them in favor of the project's existing tempo (or tempo map if it already has more than one fixed initial tempo). Either way, you can save as a "Normal" project file, so starting by opening the MIDI file is probably the way to go. You can then edit the tempo in the Tempo View as needed. 
 
If you have an existing project or template that you want to bring the MIDI fie into along with its tempo changes, you can open both that project and the MIDI file as a second project simultaneously, and copy and paste the MIDI clip from one to the other using Copy Special (Ctrl+Alt+C) and Paste Special (Ctrl+Alt+V) to ensure tempos are included.

Thanks for the assistance, much appreciated. Will work on those options and update on progress.

Thanks, I learned something new, which happens a lot for me in Sonar these days.
 
Altho I must admit to reading the title as Midlife at first glance!

charlyg
Altho I must admit to reading the title as Midlife at first glance!

The problem I had is now solved. The option I used was to copy and paste the midifile from one project to another with copy/paste special. Thanks brundlefly for your help and also promidi and mettelus for their contribution.

Cool. Glad to help.