I just upgraded to DT Register 2.7.2c and I can no longer create events. Everything seems to go fine until I save at which point I get a red x net to the start date/time field. I get that same error whether I create a new event or link to a Jevents event.
pbruce - which user account is your license associated with?
2.7.2 is long not supported. If you just upgraded to a version that is so old, makes me wonder where you got it. That's why I asked the above question.
Based on that, I'm assuming you have no active license. You need to purchase one so you can get the current version in place and have a year of updates and support.