User Profile option returns error

A customer reported that when their users try to click on "User Profile" in the user menu, that it returns an error (a 500 type error in the browser). I tested this and found it to be true.

the URL it's going to is www.mywebsite.com/my-profile .

I tried just about everything I could think of to remedy this.

I re-assigned the menu item and saved it.
I changed the user level to Public (I had it set to Registered).
I tried putting the option in the main menu.
I tried resetting the menu module.

I reviewed the Configuration to see if there was anything there, then ran all the Tools to be sure the database was okay.

I'm lost on this. What could be causing it?

Thank you,
Ernie

Try enabling debug mode and maximum error reporting in Joomla global configuration then retry to see if any errors output. If unable to see any fatal errors try disabling non-core plugins 1 by 1 within CB > Plugin Management.

It reported the following error:

Fatal error: Cannot declare class DtregisterModelEvent, because the name is already in use in /home/mysite/public_html/administrator/components/com_dtregister/models/event.php on line 93

It seems to be a conflict with DT Register, but I don't know what the error means. I've contacted the support people for DT Register to see if they can help.

Thank you,
Ernie