Have a look into your account, usually this happens when your click bid is too low. Have a look at the keywords and see if they are active, if they are i would increase the bid slightly.
Agreed. I do not know if there is any truth in it but it appears (from a number of similar posts here) that new campaigns may need a "kick start" of much higher bids to get them going. Then, after a day or two, once the AD-bot has crawled your site, calculated relevance and QS, and your ads have a "settled" position, the bids fall back to a more realistic level.
i have had this problem before if they dont keep showing just email google adwords they will have your ads showing