I had a similar issue with my Sam 440ep and this is what resolved it.
Sam 440ep's are very picky as to what video cards work in the fast PCI slot (the top one.) I had a Radeon 9250 like you have and this the solution that worked for me.
Move your graphics card down to the second from the top slot and try booting your AmigaOS 4.1 install CD.
Good luck.
PS. I noticed you had a second graphics card you might want to try that one in the fast slot.
