3.0-r1 ipchains problem (kernel 2.2.20)

["Franco Galian" <fg@lhs.com.ar>]

Hi, I'm having trouble with a kernel update.
First of all, I'd installed a Debian 3.0-r1. Everything worked fine, except
for ipchains.
When I tried to run ipchains -L, the following message appeared:
 "ipchains: Incompatible with this kernel".
After doing some research, I decided to upgrade the kernel to a 2.4.18.
After making that selection using the "dselect" utility, and rebooting, now
the system doesn't boot anymore
It says something about "unable to mount root...".
What are the steps recommended to upgrade that kernel? Should I boot from
the rescue CD?
Anyone had a similar problem with a 3.0-r1 release?
Thanks in advance,

Franco Galián