Running Win 7 HP 64Bit, AMD,4GigRAM, 320 HD, and using Seagate 1TB GoFlex external: When reaching 25% of the backup the computer locks and has to be rebooted [w/o completing a back-up]. I have tried Acronis TI 2010 and also the trial version of Acronis 2012 with the same results.
I have installed the 2010 version w/o issues on several other computers. I posted over on the Acronis thread, but no response.
Try colonezilla, or if you think it's the drive, use that same drive on the other computers. Could be the computer hard-drive as well. Run a BIOS or low-level hardware scan on the PC hard-drive (not just check disk from Windows).