I think my problem might be with how I have the items set up in the group. It looks like the date I compute in the action item never makes it into the insert statement. I’m guessing those empty items are what are giving me the DateTime overflow errors.
After realizing this I tried to assign the results of my action items directly to the table fields but then I just get errors about the fields being null.
So, how does one go about setting up action items which compute items mapped to table fields?
Thanks for hangin’ in there with me through all this! 
–HandledException