Error ThinApp - WHAT is IT?!

Switched to Windows 10 from 8.1 and one of my once portable programs at startup was producing an error
ThinApp has encounrered an unexpected error. Click Abort to close the application, retry to debug, or Continiue to ignor the error. Suport info; PID=4084, Wow64.cpp@483
Thought it was a feature of Win10 but nifiga! It turns out such messages many people have been popular. True answer the question I have not found.
Can someone tell me what it is?