rebug help

I installed debug 4.21 on to a ps3 I have. That ess fine. But I installed toolbox and it just comes up with a black screen, same with multi man. I gave a bluray drive but it's off another machine, I will remarry it. So I tried to downgrade to rebug 3.55. It did 999 fine so am on that at the mo, but it says 3.55 is corrupt and won't do it. also get black screen if I try toolbox and multi man
I'll try downloading 3.55 again when I finish work but does anyone know why I get a black screen?
Also if I use 3.55 to put it in factory service mode, will I be able to do the bluray remarry without a dongle