I have found a few posts about different runtime errors that appear to have been fixed.
I am still experiencing the issue, it happens when i start Mezzmo.exe regardless of whether the Server is running or not.
Capture.jpg
The window appears as per attachment. If i select OK or close the error window it closes the Mezzmo program. The server still runs if it had been started.
If i ignore the window, Mezzmo may run ok or it may crash.

I am running a registered version 2.7.1.0 on a Window 7 64-bit PC