Why is it ONLY Sonar (NO OTHER APPS I HAVE) that insists on changing my sample rate from 48k to 44k for NO REASON AT ALL!  I establish the sample rate in my interface s'ware, then when I boot up a file THAT HAS 48k as the stated sample rate, it just reverts back to 44k!

The project dictates the sample rate. You don't want to listen to 44.1 played at 48. You can set the default rate for new projects.

44.1K is the industry default for CD's.
 
While you are able to set that rate to anything you wish (from the options available) the industry as a whole uses 16/44.1K for commercial audio CD's. Referred to as "CD quality audio".
 
My best guess as to why Cake sets the default to 44/1 would be for that reason. It's the standard.
 
I know some other aspects of parts of the industry do request different sampling rates....so cake provides the ability to record and convert to those differing rates in the event you need that rate...

It's unlikely that SONAR changes the sample rate "for no reason". SONAR in fact cannot change the sample rate at all. It can only make a request to the driver to make a request to the interface to change it. Ultimately, it's the interface that decides the sample rate.
 
Many interfaces, including my own MOTU, default to 48KHz when they're first turned on. Others default to 44.1KHz. The first time you run some audio software such as SONAR or Windows Media Player, that software will request a sample rate via the interface's driver.
 
I think (don't know for sure) that SONAR does this just once, when the project is first loaded. If the sample rate were to be subsequently changed by some other software while SONAR is still loaded, you could end up with an incorrect rate.
 
Maybe I'm misunderstanding the scenario. When you saying "boot up a 48K file" does that mean opening a 48KHz project, or importing a 48KHz file into a 44.1KHz project?

THAT's a fair question BittFlipper.  Thanks for chiming in.  I've preset the default PROJECT sample rate at 24Bit/48k.  (BTW, all the CD stnd info has nothing to do with this issue. My interface is 24Bit/44.1-192k).  The Bit rate doesn't change like the sample rate is.  Also, whenever I'm NOT in Sonar the interface stays on 48k just fine, and as I mentioned in the opening post, Sonar is THE ONLY DAW app out of 4 that I have that does this.  It doesn't change until it's finished loading all of the VSTi's, and if the audio engine is off it will stay on 48k.  Which BTW, If you would be so kind as to check out my other post I've just posted re: my VST softsynths.

I am pretty sure there is a Cakewalk plugin that will not work at 48 kHz. I have had this issue where I wanted to do a project at 88.2 kHz and Sonar wouldn't work because of a plugin. Please provide a list of ALL plugins used in the project in question and I will tell you if it will work @ 48kHz.