cPanel solution: 'An error occurred in the upload. Please try again later.'

I too suddenly got the dreaded message: ‘An error occurred in the upload. Please try again later.’ I went through all the solutions offered in every post I could find, and got the same bad results.
In my case, it turned out it wasn’t a WordPress problem at all. The source of the problem was the ModSecurity Domain Manager that my host had installed recently.
ModSecurity is accessible through cPanel. I turned it off, and the file upload went just fine.
Hope this helps someone out there.