When you say "green screen" do you mean the MFS assert (or GSOD) screen
? Or is it just a blank green screen?
As Scandia mentioned, it can take a while for TiVo to diagnose and fix data corruption or isolate bad sectors on your hard drive...several minutes to several hours depending on the severity of the problem and/or the size of your hard drive. But if the GSOD screen remains for four or five hours odds are that it can't recover. That usually means your hard drive will need to be replaced.
You could try some of the other Kickstarts
to see if one might help.
Best of luck!