eshark - 6:20 pm on Feb 2, 2005 (gmt 0)

One of my keywords gets about 1500 impressions a day with CTR about 2%.
This morning noticed that the number of impressions was 2600 and rising and CTR is about 0.1%. I've used this keyword for months and it NEVER got more than 2000 impressions a day, CTR has always been stable. ANd now it looks like it's gonna get 5000 impressions.
Is that a google bug? Any ideas?