I also encountered this problem after upgrading to the 2008 OS. My N800 had been remarkably stable prior to that (uptime of a couple of months), and then the battery life dropped to hours instead of days. There were no obvious culprits (I was using the same access points, or no access point, and auto-connect was off).

I haven't had much free time, and was just gradually restoring my customisations when I could, and then the problem suddenly went away. I'm pretty sure what did the trick was adding a "-c" argument to the metalayer-crawler startup, but I haven't had the time to verify that this was really what did the trick.

More specifically, I think the problem went away went I edited /etc/init.d/metalayer-crawler0 to pass the following option to the daemon:
Anyone else having this problem might want to try something similar.

Cheers,
Lon