Re: Ubuntu 12.10 usb transfer issue
NTFS writing is heavily CPU-bound on Linux.
What this means is that write speed to an NTFS hard disk will depend on how powerful your CPU is, and while writing to NTFS your CPU will be running at full steam.
This is okay, it's not dangerous and won't damage your hardware.
But it sounds like your CPU is gradually overheating. You might have dust in your CPU cooler, or simply not be able to dissipate the heat from your CPU running at 100%; this is a bad CPU cooler/fan if it can't do that. When the CPU starts overheating, it purposely runs at a lower speed to try and generate less heat (this explains the copying slowing down), and eventually if the heat keeps rising the CPU will automatically shut off to prevent damage. This immediately halts the computer.
Best thing to do is check your CPU cooler or have an experienced computer hardware person take it off and check it or replace it with something better. Your second-best option is to format your USB disk to ext4 or fat32. The latter cannot store files greater than 4 GiB.
I try to treat the cause, not the symptom. I avoid the terminal in instructions, unless it's easier or necessary. My instructions will work within the Ubuntu system, instead of breaking or subverting it. Those are the three guarantees to the helpee.