It is also worth noting that this problem is not restricted to relatively small usb sticks. I have the same problem copying large (30GB) files to a 1TB external drive. When you have a drive that big - or bigger - 30GB files are not at all unreasonable. I've started booting with Fedora to copy my large files, and I see the problem to some extent there, but it's nowhere near as bad as the recent Ubuntu issues, and it doesn't freeze.
It is also worth noting that this problem is not restricted to relatively small usb sticks. I have the same problem copying large (30GB) files to a 1TB external drive. When you have a drive that big - or bigger - 30GB files are not at all unreasonable. I've started booting with Fedora to copy my large files, and I see the problem to some extent there, but it's nowhere near as bad as the recent Ubuntu issues, and it doesn't freeze.