Gain very low almost nothing but been fine before help!!

Hi, I've been using my MXL 440 vocal condensor, Alesis iol2 mixer and Logic Pro 9 on my Mac Mini set-up fine for a number of months now but recently the gain has suddenly dropped so much that it hardly picks up audio at all (but it is just about audible if you shout into it with the gain turned up full on the mixer). I've managed to get around this problem a couple of times by restarting or creating a new project, but it has since happened again and these things aren't working any more. As I said I don't think its a prbolem with the mic or mixer as they've been working fine with logic for ages, and I never had a similar problem when I was using this set-up with Cubase. Its almost as if its detected a very loud noise maxed out and then re-set its gain very low for safety or whatever. I have no idea what to try now so any help would be greatly appreiciated!!