Kernel panic: VFS: Unable to mount root

[Jimmy B <broderb@home.se>]

Hi list!
I just compiled a new kernel version 2.6.8 with sources downloaded with 
apt-get:
apt-get install kernel-source-2.6.8
I ran these commands:
make mrproper
make menuconfig
make
make modules install

I do upgrade-grub and it adds the new kernel to the menu.
When I rebbot using the new kernel I get a kernel panic:
kernel panic: VFS: Unable to mount root fs on unknown-block(0.0)

I'm thinking maybe I missed enabling something in 'make menuconfig' but 
maybe I'm wrong? Any suggestions/pointers to what I should be looking 
for would be appreciated.

/Jimmy