Studio Instruments (Bass)- Sonar incorrectly reading notes?

When I create a bassline using Studio Instruments (Bass guitar) on Sonar Le 8.5, the playback does not match what is written in the piano roll or staff.  For example, I created a bassline that had four measures of eightnotes; during playback, it will skip several notes resulting in a choppy/syncopated rhythm that does not match what I have written in the staff. This happens when I changed it all to quarter notes as well- during playback, it would randomly skip every other note or so.  Any ideas on how to fix this?  Feedback would be much appreciated!