Same issue here. I'm to the end of my rope at this point. I've done soft and hard resets, validated all settings - absolutely nothing running (no wifi - nothing) on the axim and still the battery is dead in short order. I'm certain at this point that there is some issue in wm5 with the axim that is causing the quick battery death.
I like being on the edge of new software releases and I am willing to suffer a reasonable amount of pain, but this is beyond my patience level. I've been checking Dell for any update, but so far nothing but the link on how to go back to the earlier 2003 version of pocket pc. Thinking that at this time that maybe my only option - I can always upgrade again to wm5.