It is either a corrupt file. (If it's a compressed file, open with winrar and if it gets any errors it's corrupt) Just copy over any file, (You can use notepad to just write a few letters to a .txt file then copy it, if it copies, then your original files are corrupt.
If it doesn't copy, re install your USB port driver (You can also just test another USB MTP device)
Try using PTP, rebooting, and trying again.
Use a different cable. Roll back to a previous rom (Not necessary but try anyways).
Tell me if this fixes anything
Also try using your phone with another computer, also switch cables while using that other computer to see if that's an issue. if it works then it's a computer related problem that should probably be fixed by re installing your usb port drivers or re installing windows (bit drastic but its a last resort)