2.4.28 is out, so I've rolled up a new kernel. It also includes the latest UML patch, and a special patch which is required to allow UML to exit properly under hosts > 2.6.9. So, this is in preparation for the upcoming host kernel upgrades.
If you're on host33 or host34, rebooting will only get you into 2.4.27-linode34-1um. A bug in the host kernel will prevent you from running anything newer than that. So for you guys, "Latest 2.4" points to 2.4.27-linode34-1um.
How to Upgrade
See if you're already running 2.4.28-linode37-1um by viewing the output of "uname -a" inside your Linode. If not, follow this procedure:

Log into the Linode Platform Manager (LPM)

Configuration Profiles --> Click on your configuration profile

Make sure the Kernel drop-down has "
Latest 2.4 Series" selected and Save

Reboot your Linode
Thanks and enjoy!
-Chris