I have a similar problem, also giving error 4000
Problem occurs only when using M.C., not in Total commander or Win Explorer.
Copying any file(s) to a external HDD (USB) giving the error.
File can be a txt file or movie files, just anything, and the problem occurs.
Did already format it twice, without any result; when I read this post, I tried Total Commander... no problem.
System is a Medion P7300/Win7.