If you are using a class inherited from IterativeRobot, note that there is no built in delay, so it will use as much processing power as possible, the kernel splitting it equally with tasks of the same priority. To correct this, you can add a taskDelay() call in each of the XXXContinuous functions.
The delay should be long enough to cede as much processing power to other threads as possible without being so long that you are missing calls to the XXXPeriodic functions. (Assuming you are not using the XXXContinuous for anything time sensitive.) Make sure to include taskLib.h which declares this method.
Here is some documentation on
VxWorks tasks if you are interested in reading more.