You can see my equip in my signature, and none of my other DAW s'ware has this problem.  When I open some of my projects in Sonar, and I already have my interface,  my AUD.INI file, any WAV files, etc on 24Bit/48k, and during the time the project is setting itself up at the very end, it switches to 24/44k.  All my drivers, etc are updated as well.

For me it will change if the original project was that rate. Once a project is saved it cannot be changed without a major lobotomy. 
 
I only get this because a lot of my old stuff was recorded with a different interface which was using 48. I have to use 44.1 if I'm using my Yamaha 01v mixer. 

With existing projects, it does not matter what the interface, AUD.INI or wav files are set to, SONAR will read the sample rate from the project file and configure itself accordingly. This sounds a lot like this thread http://forum.cakewalk.com/FindPost/2819494