This topic has come up many times over the years. I usually see this problem whenever I open and disturb the boards inside my 3000. In my case it seems to be caused by a marginal connection somewhere in the Zorro riser. I have had to pull apart and re-assembly mine upto a half-dozen times to get it booting again after adding a card or cleaning dust. Sometimes, lifting it a half inch and letting it fall seats everything.
After I get it booting again, it normally runs fine until dust plugs it up again (1 or 2 years).
Don't give up!
