We have a problem identical to this one listed by user sabdoo on your forums:
http://www.dthdevelopment.com/index.php ... ails#p5141
in particular, concerning already added events, the "Maximum Group Size" and "Send New Registration Notification Emails To" fields which were properly filled out when we published the new event, showing '0' when we edit them.
We were using version 2.5.8b, and in an effort to fix this, upgraded to version 2.6.3a. We have followed the solution you provided at the end of that thread, and it has not worked.
I tried to submit this as a ticket, but the ticket system just kept repeatedly telling me that the code I entered was invalid, even when it was entered exactly. Contact me for required info.