X won't start after building new kernel
 

I just upgraded my redhat 9.0 installation from 2.4.20-18.9 to 2.4.21-rc7-ac . Everything compiled/booted fine, except that running "startx" results in a loss of the video signal to my video card. Also, trying to run "XF86 -configure" gives me a Signal 11 error. It's a radeon 8500 card.

are you using a floppy boot?
I have found that the 2.4.20-18.9 kernel does not support nvidia drivers, so I will have to wait till nvidia releases a new driver, it might be the same for the radeon card. If you are using grub or a bootloader, then just pick your previous kernel, if you upgraded (-Uvh) then you are screwed, when upgrading a kernel, you should always pick the install instead of the upgrade since it is not good to replace the previous kernel.