HI there
I dont know if this is right...but i had a similar problem at work once.
The problem was that the "path" was too long, meaning you had to go through too many folders to get to your file or the name of the file is too large.
I simply had to create a new folder, creating a short path and should work.
aka instead of having...Documents>Pictures>Another>Another1>Another 2>File
Just have Documents>File
Just upload from there, and should work.
Like i said, i might be completely wrong and Al will probably know but may work.
Good luck...