This may sound strange, but with some of our installs, we have found that if it is not the generally accepted fixes (for flashing red) such as a bad power brick, firmware, or cabling - then the disconnect/reconnect issue has turned out to be either 1)the video splitter is incompatible (if you are using one), or 2) The video card driver. We have had instances wherein the actual video card driver was causing this issue. These problems were on Dell systems with the factory installed video. The other issue, with the video splitter, (odd as it seens) actually caused the board to constantly disconnect, then reconnect - over and over again; there was no flashing red in this case though. Just remember that when the problem isn't solved by the regular means - it's possible that something 'irregular' is causing it. We've installed over 2500 boards in the last 4 months - so we've almost come across everything. That said, I'm sure we've not seen it all - and something new will arise before long.
AJ