Well that was disappointing. Booted from a live Ubuntu USB and it took about 8 hours to run badblocks on everything - nothing was found. So next steps will be to try different SATA ports on the MoBo as someone suggested. I also have another similar horsepower computer I just bought from someone that has no HDs so I may try that as well. Odd that this would all start with an OS reinstall though, which makes me suspicious of HW issues on the mobo or elsewhere. I also got this similar error message to the original one posted, but about radeon which suggests the graphics card which suggests afterall a mobo issue of some sort https://imgur.com/gallery/33afTD4