TOPIC: New Event Creation Error (500)

Hi,

I just purchased and installed DT Register

I have:
DT Register 2.7.23
Joomla 1.5.25 Stable
using PHP 5.3.6

Install seemed to go smoothly, and I set up an event category fine, but when I clicked 'New' to add my first event, I got:

500 - An error has occurred.
Internal Server Error

on a new screen.

Did I miss installing a part of the modules, or is there something else I'm missing to help this run?

Thanks!