I've had some screw ups in Linux but so far I think this one beats them all.
I compiled kernel 2.6.15.4 this evening and now my file system can only be mounted as Read-only. I was using ext3 as I recall and I thought that it should be compiled into the kernel. I noticed that it was set to be compiled as a module so I changed this (pressed "Y" in the make -menuconfig).
Then I rebooted the system so the new kernel could load and then I could (finally) recompile my nVidia drivers (I had upgraded gcc between the previous kernel compile and the current attempt to install nVidia drivers, and I couldn't get it to work...).
What happened was a bunch of error messages telling me that the file-system was Read-only. All my files are there but I can't edit them. I couldn't even log in as root.
I have older versions of my kernel saved, but when I tried booting with these, it said there were unrecognized options for the file system. Um, then the kernel panicked.

Clearly, I need to get get the filesystem to be writeable so I can get back in to recompile the kernel with better options.

I'm *REALLY* stuck on this one. Any help? PLEASE!!!???

A) If you use grub, enter the grub shell and manually select your previous kernel and initrd file. Then change your menu.lst file to boot with the old kernel.
B) If you use lilo, boot up into the rescue system or a rescue disk and edit the lilo.conf and run /sbin/lilo.

Heh..... the problem seemed to resolved itself. I rebooted into the new kernel so I could write down the error messages to give a better description, but... it was able to mount the filesystem properly! then it ran fsck, fixed a whole bunch of problems, and my system's working fine again.

...weird, but at least it's resolved.