I've upgraded a WSS 2.0 site to MOSS 2007 to Foundation 2010 using the content database attach method, and I have a vacation calendar where I can see all the events in the list view, but the events do not show up in the calendar view unless I edit each event and save it. I've tried creating a new calendar view and that didn't work either. Any ideas how I can get the items to display without touching every single one?
This may not be the most ideal solution, but it has worked for me in a similar situation: in MOSS, save the list as a list template with the content included. Then create a new list from that template. It will re-create all of the items in that list when you do so.
The downside of doing this is that it will set you as the person who created the list items and the current datetime as the created datetime.