I was able to export MP3s using the audio generated on Cakewalk Platinum.  Now I can not without upgrading and or unlocking the MP3 encoder that supposedly must be purchased from Cakewalk! Out of shear frustration I went to mthe Cakewalk store and spent $9.95 for the Cakewalk MP3 Encoder.  As I tried installing it an error message suggesting that the Shared Utilities folder could not be found and that I must first install my Cakewalk product ... Platinum ... which, of course, is already installed with it's Shared Utilities folder present and intact!  I gave up and asked  the bakers for my $9.95 back!  Meanwhile  I would like to know if there is a more straightforward way to export MP3's directly from Platinum without first exporting a wav file then going to something like Audacity to convert to MP3!  

I suspect you purchased the wrong product. Cakewalk will replace it with the correct product. This post describes the two products http://forum.cakewalk.com/FindPost/3273106 

Thank you for your prompt reply.  I am however, completely dismayed over the way Cakewalk manages it's software, its installation instructions and its customer support. (This forum, however, is exceptionally good)   How is one to know what the heck to buy?  I only bought it because I didn't have the time or inclination to go through the Customer Support site and wait (maybe days) for an answer!  The site you referenced just adds to the confusion?  Do I want to buy the Activation Package?  or do I want to buy the MP3 encoder package?.  Gosh ... maybe I need to buy both! But at the same time there is no mention of the SONAR Platinum DAW for which I need the encoder.  Maybe the encoder is already packaged with the higher end products but there is a bug in my particular product.  
I'm ready to give up (I've given up) on Cakewalk support!