Amiga os4.1 Install problem

[ozkano]

I try to install os4.1 to my amiga 1200, it gives black screen after showing amiga os4.1 screen, here is my config

a1200
ppc 210 mhz with 128 mb ram
mediator with radeon 9250 128mb graphic card

I boot from floppy with cdrom, it loads kickstart reset itself I am getting all video from radeon, is there any way to install os4.1 from aga

best reagrds