My guess is you have a keyword that performs well usually but has suffered a dramatic reduction in impressions for a day/few days. If this is so it should return to normal delivery within a week of the problem arising.
If it's a different scenario then we (and Google) would like more details so it can be avoided/fixed.
2.9% CTR ,Avg. Position 4.0, Impressions approximately 194,000, clicks approximately 4,000.
In the old days keywords simply stopped running when you didnt meet certain criteria. But my understanding is that with the implementation of the new active/inactive regime, you had an oppurtunity to reactivate a keyword by raising the bid. The word is still active, its just not getting any impressions.