I saw the thread about the error:
Fatal error: Method name must be a string in /home/nawboclv/public_html/cms/components/com_dtregister/controllers/payment.php on line 104
from March 2012. it shows as solved, and references fixes in 2.7.15a.
but i have one user who is getting this error and we are on 2.7.16a.
We've had 10 other users successfully register for the same event, and i am trying to get further details about what this user might have done differently.