I am using DNN 4.3.7 and Form Master 1.5.4 and I'm having great difficulty in getting the Upload file function to work on any of my forms. Attempting to upload a valid file makes the module unavailable. Can you help?

Check this thread first.

I have checked and implemented that recommendation, but unfortunatley it doesn't remedy the problem.

The next step is to explain your entire setup

Version for all software

File type and size you are trying to upload

Connection Speed

Browser and Version

Have you tried this from multiple machines?