This is not a sonar issue, but a sound card issue. I can load and play projects in 16 bit, 24bit, 44.1kHz, 48kHz, 88kHz, 96kHz and 192khz and i get no warnings. My sound card drivers change to the project at hand.
Your issue is caused by your sound card not having drivers written to change sample rates at will. most sound cards made for recording can do this. Obviously, your cannot.