Welcome to LQ. I'm not familiar with Gentoo, but you can regain some control over your laptop by booting from a Live CD, such as Knoppix. Knoppix is "Linux on a CD", and will allow you to run Linux on your machine without using the hard disk -- everything runs off the CD. This is an excellent tool for getting Linux back up and running on a hosed machine, and the main point is that it will give you the ability to open up a terminal session so that you can do some repair work. Knoppix is available for free download at
LinuxISO
Note that you will also need your CD to be the first boot option in your BIOS. Boot is up, and Knoppix will load (which is a very cool distro on its own BTW) and then you should be able to open up a terminal session to do the repair work.
I can't say what the true cause of the problem might be, but if the problem started happening immediately after you started using the new kernel, then the new kernel seems like the likely suspect. Assuming you've still got the previous kernel, just change your bootloader to use it rather than the new one, save your changes (and rerun /sbin/lilo if you use lilo) then remove the Knoppix CD and reboot. If all goes well, your laptop will reboot using the original kernel. Hopefully that should do it. Good luck with it -- J.W.
