* Daily Budget is now way less, allowing ads to shown way less?
* Max CPC is lower, and ads are now languishing on the second or third page?
* Ad is disapproved? (This will certainly do it! ;)
* Keywords are of a sensitive nature, and not yet reviewed/approved in their new Ad Group - whereas they were before?
AWA
Max CPC is lower, and ads are now languishing on the second or third page?
You might have also had a high CTR on the keywords, and you lost it when you recreated the keywords. Either way, it will push you to the back pages.
Also, you could have been seeing the majority of your impressions on search partners. Your ads won't go live there until they are approved.