Have you ever hit the "D" key only to get the Preferences window? It happens to me once in a while. This is just one of many oddities that happen only occasionally.
 
 
Steve

Change your computer keyboard :)

No but seriously, it could be that some chip in your computer keyboard is acting up.
Once it happened to me and it was driving me nuts and blamed everything underneath the sun until I changed the said peripheral, and everything went back to normal. 

Is very possible, tho Sonar is the only app this happens in.
 
 
Steve

^haha I had that happen to me a long time ago,  every couple minutes no matter where "something" would type a single "p", cue me scanning for virus and backdoors..

I booted from a Knoppix DVD and it still happened, turns out the usb controller was dying on me as a couple days later everything usb just stopped working.