Since firmware changes aren't helping your button issue, it might be time to power down the unit, get out a screwdriver and open it up. But only if you feel comfortable doing that, of course. There's a chance that you have a poor connection involving the cable(s) that connect the button assembly to the processor board. I know it's not the first thing you'd check, but it would easily explain why the buttons aren't working. Small chance, but worth investigating if only to rule it out.
