Further to Steve's discussion relating to GRUB, I've also been battling with that particular beast. My test machine is probably a bit of a mess from that point of view because I've upgraded through about 3 versions of Mepis now rather than fresh installs, which is the recommended route... Somewhere along the line, newer kernel versions have gone from looking for /dev/hda to /dev/sda. To correct for this, I've gone mostly for the option of putting UUIDs in my /boot/grub/menu.lst.
What brought this to a head was a recent upgrade of the 2.6.36 kernel I was using. This seemed to kill my Edimax EW-7318UG's ability to get a DHCP lease. (I've posted about this in the main networking forum, amongst other places.) I tried both the Liquorix and Mepis 2.6.36 kernels and both failed to get me a wireless connection. Fortunatly, as my test system is an upgraded mess, it has got a few older kernels still installed. So, I'm currently running a Mepis 2.6.32 kernel which works perfectly! As I mentioned though, I had to go through GRUB manually to get all the available kernels to boot so I could find one that works...