Quite honestly, I wouldn't mess around w/ anything but CAT 6 at the most. Even Cat 5e is likely sufficient if the run isn't too long. With CAT 8, you're making things unnecessarily complicated, esp for only 1Gb. I'm not saying it's definitely the source of the problem, but I'm always suspicious of relatively new standards combined w/ old tech. CAT 8 is overkill here, in the extreme.