You've got some unusual behavior going on, for sure.
For anyone to be able to help you, we will need to know something about what you are working with.
Which Sonar version?
What is your OS?
What effects, limiters, compressors, etc., do you have in your busses or tracks.
Is it just this one project?
Have you experienced this before?
Have you made any changes to your system? MS updates, new plug-ins, anything?
Have you tried rebooting the computer?
Do you turn the computer off, or let it go into sleep mode when you are not using it?
Sleep mode, especially with XP, can lead to some unpredictable behavior.
Give us something to work with, and someone may have an answer.