Problem solved, my M Audio Luna is working again. Seems that becuase the mic got cold in my garden studio, it got condensation on the capsule and started popping. Now it's dried out it is working again!
From Sound on Sound if anybody is interested:-
If you suspect that you have condensation problems, the only solution is to let the mic dry out on a shelf above a radiator or in an airing cupboard. While professional studios are unlikely to have condensation problems caused by the studio environment itself, garage studios and studios set up in basements are more likely to fall foul of this problem, so ensure that they are properly heated and store your mics somewhere reasonably clean, warm, and dry.