kidder - 8:57 pm on Mar 13, 2007 (gmt 0)

"I'm thinking bigger than mere corrupt data, kidder - more like a buggy infrastructure change. They may be trying to accelerate the pace of indexing and are not getting the coordination of events handled properly. That's pure guesswork, by the way."

Tedster - history tells me that your guesswork is a safer bet than mine. I will add that today my site has popped back into the top of the serps just like clockwork - that makes it now 3 weeks in a row it vanishes on a Monday and then is back by Wednesday. It's almost predictable, something new that I have not seen in the past.