Re-install MacKeeper (the demo version should do nicely), restart your computer, then uninstall MacKeeper using the procedure here.
This didn't work. In fact, after I did that and restarted, the machine went into a cycle of restarting every five minutes with the grey screen and the Apple (no spinning device) between restarts.
After 20 minutes I gave up and forced a shutdown.
ryck
"What Were Once Vices Are Now Habits" The Doobie Brothers