Has anyone come across these situations?
Yes, I see it occassionally and Outlook 2003 used to do it as well.
Not sure of the technical explaination but bits of Outlook can be running in the background when you're not aware. If you shutdown the PC, then the shutdown forcibly kills various processes & in Outlook's case the local copies of data are left dirty by whatever process was running in the background(usually connected with network access). I'm sure there is either an MS KB note around somewhere, or one of the dev team might have blogged it.
I don't worry too much about it, I just let it clean up and carry on in it's own sweet way.