The instalation of the new kernel may have missed some configuration on the sata support, to recompile a kernel of your own you should download the latest version from
www.kernel.org and look for a tutorial on compiling a new kernel which is kinda hard if you have never done that before, but there are a lot of tutorials around which can guide you trough it and some special ones for sata drivers
http://gentoo-wiki.com/HARDWARE_SATA
here you can look how to add sata support when compiling the kernel, I hope this gives you a little help, it got my sata drive working great