Well to be honest its not broken in 8.1, at least not for anyone else. I mean you can try it if you want, but betas are just that, beta, and will likely have more bugs than the stable version so I would advise against it at this point as you don't want to introduce something that may cause more, but unrelated issues that may confuse us solving this one.
I don't want to repeat myself but have you tried another drive to see if its a system wide issue, or just a drive issue?