I copied this info from Cakewalk's FAQ Site section. If you do a search in Sonar's help menu, it should tell you in more detail, but if you still have problems let me know).

"Load the "Turn GM System On" system exclusive bank (GMSYSTEM.SYX in your Cakewalk directory) in the Sysx View, and set the bank to "Auto Send". This message will re-initialize a General MIDI compatible sound module to a known state".

Ron