622 reboots when transfering to ehd

For about the last week or 2 when i transfer programs from my 622 to my external hard drive (WD My Book Essential WDBAAF0010HBK-NESN) the dvr will reboot when i transfer programs longer than 2 hours in length. The 622 will start the transfer but about 1/2 way through will shut down and reboot. Programs around 1 hour transfer ok. Is anyone else having simular concerns? I have been using this drive for about 7 months with no problem till recently.

I checked temperatures, did not appear higher than normal. I switched from the rear usb port to the front port and did not have any problems. Reciever must be going bad.