unable to mount root filesystem

[Leo Spalteholz <leo@thewoodpecker.ca>]

Hi,
I recompiled my kernel (2.4.19 for k7) and am now getting an error 
about not being able to mount root filesystem and a kernel panic on 
boot.  
In my grub menu.lst I have
title		Debian GNU/Linux, kernel 2.4.19-k7
root		(hd0,4)
kernel		/boot/vmlinuz-2.4.19-k7 root=/dev/hda5 ro
initrd		/boot/initrd.img-2.4.19-k7
savedefault
boot
which works fine (this is the stock debian kernel image)
and for the compiled kernel I have:
title		Debian GNU/Linux, kernel 2.4.19
root		(hd0,4)
kernel		/boot/vmlinuz-2.4.19 root=/dev/hda5 ro
savedefault
boot
which gives me the kernel panic.
The root is the same so that can't be the problem..  
ReiserFS is built into the kernel (thats my root filesystem) so thats 
not it..  Could it have anything to do with initrd?  I disabled it in 
the kernel config.
What else can I check for?

Thanks,
Leo