If the keyboard isn't working in Safe Mode there's a larger issue involved here.
I presume that the keys are working when you go to select Safe Mode (or do you get into Safe Mode another way)?
This is, IMO, a compound error in your OS (In other words, there's an error causing the black screen, and a separate error causing the keyboard not to work. Is it possible that the system is infected? Had you done any scans recently to rule out malware?
Can you get into the Repair mode by using your Installation DVD? To do this, boot from the DVD and select the language options in the first screen. In the second screen, select "Repair this computer" in the lower left portion of the Window (don't select anything else as you may wipe out your current installation).
Run Startup Repair to see if it'll fix the issues enough to get into Safe Mode.
After that, run it again to see if you can use System Restore to restore back to a time before this (the black screen) was happening.
FWIW - Most black screen errors that occur after Windows has started loading are due to bugs in drivers
. But, it can also be caused by problems in the Registry. System Restore will take care of the Registry errors if you go back to a time before the error started.