Are you on a mission to post your site links in every response Jim? Appreciate the updates but watch out that you don't fall foul of the mods here.
Yep i've been noticing this for a few days, it always occurs around the time of a page rank update and I think that Google are getting much more picky, which is probably a good thing
These changes are the norm. A year from now it will be useless to keep track of individual updates/changes as google becomes more versified and will automate updates daily. Updates could be come a daily event or even more than once a day.
I was wondering why I didn't noticed anyting since I red this thread and... surprise! webmasters tools has just shown me a lot of changes in Top Search Queries for a new site (only 2 months). I can't wait to see analytics tonight!