Do you mean you can't see the guides that you create by dragging out from the rulers, or that you can't see the actual rulers themselves along the top and left edges when you turn them on under the View pop-up menu?
Either way, have you check that all the appropriate items are turned on under the View pop-up menu at the far right of the Canvas?
And have you tried trashing your preferences file?
1) Quit Motion.
2) Navigate to User/Library/Preferences.
3) Locate com.apple.motion.plist and delete it.