I just recorded a vocal for the first time in X3.  All I hear is squeaky noises that make me sound like a chipmunk.   And then the vocal recording completely drops out half way through. Two different mics do the same thing and  both mic inputs on my M-Audio Fast Track Pro also do it.  All the instrument tracks are MIDI and they all sound fine.
 
Using Win 7, Intel i5.  Anybody experience this?  Thanks.

Try singing lower.

Sorry, seriously, do you have the latest driver for your Fast Track Pro? It sounds like it might be a sample rate mismatch.

Check that you're using the ASIO driver standard, and that the sample rate in Sonar matches the sample rate in the FTP control panel.

You need to stay with your current sample rate at which you started your project out at.
Example: If your project is at 44.1kHz and your sample rate of your sound card is set at 48kHz, you will get what you are describing. Both need to match what the original sample rate was
 
CJ
 

Thanks, guys, for the responses.  I got sidetracked and just got back to the project.  The sample rate was consistent at 44100,
 
But the problem was apparently that in going from X! to X3, the ASIO driver standard was changed,  I went back to ASIO and problem solved.  Thanks for mentioning that.  Weird that it would do that; didn't realize it was that critical.

A standard case of Sonar loosing the ASIO driver. This can happen when you use your on board sound and another app to play music and it grabs MME mode. If it keeps happening you may have to disable your on board audio card and only use the M Audio for all playback. The Fast track has very bad drivers so this doesn't surprise me. I used to own one and it was very undependable. A better quality interface would probably hang on to the drivers.