How long before add appears again?
Paul, to get your ad started again you'll want to go to that Ad Group and make a change to the ad itself. When you save that change, the ad will go live on Google again rather quickly.
BTW, you can then change the ad back to it's original form if you like, and save that change.
AWA
...hit on your ad. It can tell whether your ad is working or not. If it works your ad will be back within 15 minutes except there are some other reasons.
This is new to me - I'll have to test it in my own account. :)
AWA