Help: 2.6.3 Kernel Problems -- Solution?

[Ed Sutherland <digital@twcny.rr.com>]

Help! I installed kernel-image-2.6.3 and while fixing a video problem 
has completely cut off off networking, along with other commands -- the 
reason I'm writing this from OS X, not Debian.

I was upgrading from 2.18 and when installing 2.6.3 (a kernel 
supporting the iMac CRT), there was a screenful of post install errors 
about a missing command.

The questions are: 1), how do I go back to a working kernel so I can at 
least use Lynx, mail and reboot and 2), is there a solid version of the 
kernel with iMac CRT support? Thanks a million.

Ed