Comment 30 for bug 197762

I'm going to add a bit more that might be useful because this bug is driving me crazy.

It affects both my systems, one a laptop, the other a brand new desktop I purchased two weeks ago and is happening on both USB and network file transfers (via either Samba or UFS to my NAS box). I've also been experiencing occasional degraded GUI performance if I let a very large file copy (three GB or more) continue. My PC would gradually become un-responsive to the point that mouse clicks and key presses took seconds to be recognised and windows were being redrawn in slow motion. All the while, system monitor showed that both CPU's were nearly idle. When I closed the file copy window, performance returned to normal and there were no dmesg errors.

For anyone experiencing the problem, there's a kind of workaround that some people have had luck with (myself included). Try copying one file at a time and then pausing between each one to let the cache empty out, (since writing appears continue long after the copy dialog has closed). On USB devices in particular, try unmounting and re-mounting between files to make sure the file you are working on is really finished. Obviously, this is only going to work if you are copying a few large files around. If you have lots of small files to move, then zip them up before copying them and you might get lucky.