Here is what it turned out to be:
I was burning a folder full of video files. ImgBurn keep giving semaphore timeout error on one specific file. I removed that file, tried to burn, got the error on another file. So I decided that it couldn't be the files.
But, I ended up trying to move the entire folder from the original D drive (internal), to my P drive (external), and I received the same semaphore timeout error, on both of the files in question.
I deleted both files, and have been able to successfully use ImgBurn to complete the burn of the folder.
Not sure what was wrong with the files, but they were the issue.