I had a site with multiple calendars, that used list view to consolidate them for display on the main page. The 5.0.1 upgrade displayed the following error:

Events Module Updated - Exception: 04.01.00 - Message: Cannot insert the value NULL into column 'EventID', table 'twincitytc.dbo.EventsSignups'; column does not allow nulls. UPDATE fails. The statement has been terminated.

Everything I had in the Events module was lost.

Just to keep folks informed. This problem was caused due to the fact that Keith has the module from its early days, and this has brought with it a couple of interesting variants on the data sets we need to be able to upgrade against. There was blank PortalIDs in the Events table and blank EventTimeBegins in the EventsSignups table. Both of these are in theory invalid. I have now coded to deal with this - EVT-10192

We are slowly working towards making sure that the module has the correct integrity applied to it, against we aren't quite there yet. We did a major update to Referential Integrity in the 5.0.1 update, but I guess we are still in a position where some fields which should have values still don't I guess this is a task for 5.1.0 - EVT-10194

Cheers
Roger

I've got the same issue.  I've migrated my site from the early days.  I see my events in the database, but before I start troubleshooting, any way I can get them back into the new Events module?  This is extremely important! ! ! !