Michael wants to add a few additional monitors to his Mac Pro but the HDMI connectors aren't working. Leo says it's odd that the HDMI can't be used in conjunction with the Thunderbolt connector, but that could be. He should check out this tech note from Apple.
How can get a longer Thunderbolt cable? Leo says to check out Corning's Thunderbolt cables. They convert the digital signal into fiber optic, which goes a long way.
(Disclaimer: Corning is a sponsor).