Some things to try before re-timing:
Turn the needle. For my A-1, I put a pin the the eye, and turn it until the head of the pin is at about 5:00 (6:00 is the head pointing straight at you). This usually fixes it for me when it's only doing it when you are going clockwise and it skips at the 10:00 to 12:00 position.
Check your thread path.
What kinds of fabrics are you working with? What kind of batting? What kind of thread do you have in the top, and in the bottom.
Without knowing what kind of machine you have, I don't know if I should tell you to call your dealer. Mine is usually my first stop when I have problems.