Can't image: Win 7 SSD system freezes, loses disk access, reboots

I don't know if this is a harware issue with my SSD, disk controller (motherboard), power supply or something else, but depending on what I'm doing, the computer will operate for a few minutes then freeze and eventually reboot itself. When it reboots, I get the "Bootmgr is Missing" message until I cycle power a couple of times. I've tried booting from the Windows 7 repair disk and typing "bootrec /fixboot", but the problem eventually returns.

I can't get a full image update from Acronis because it hangs in the middle of the image, even if I say to ignore bad sectors. If I run the HDTune diagnostic on the SSD, it seems to always stop after about 3 minutes and always in the same spot, at 15,432MB. Is this a problem with the SSD or the disk controller?

Confguration:

O/S: OS Microsoft Windows 7 Ultimate (6.1.7601 Service Pack 1 Build 7601)
Motherboard: Gigabyte GA-MA78LMT-S2
CPU: AMD Phenom(tm) II X4 840 Processor, 3200 Mhz, 4 Core(s), 4 Logical Processor(s)
BIOS Version/Date: Award Software International, Inc. F13, 8/31/2010
SSD: Microcenter SSD G2 series 64GB ATA Device
HDD: Hitachi HDS721010CLA332 ATA Device (1TB)
RAM: 8GB