The dropping of the www is a little weird... did you have it listed that way at dmoz perhaps? or some other place where Google first came across the site? That could do it.
Maybe a submission program you used did it that way.
The jumping would happen in an area that has a lot of places crawled on a daily basis and if they change their content.
Try
www.digitalpoint.com it is a free google tracker for keywords... very handy.