Nikon 60mm auto-focus problem

[simonbarker]

Just got a Nikon 60mm f/2.8 macro lens and it seemed to perform perfectly but I've noticed when it can't lock focus the auto-focus seems to slip (for lack of a better term) and then it won't auto-focus until I switch it to M and back to M/A. I can reproduce it by covering the lens and trying to auto focus and as none of my other lenses act this way I think it's just the 60mm that's at fault.

Anyone come across this before and know a solution which doesn't require sending it off for a service?