Power management on iBook acting flaky?

[Neben Kabon]

I have been noticing that the power management on my iBook has been 
acting irregular.  Since my iBook is 3 days from being... out of 
warranty, I called Apple, who were of course encouraging me to purchase 
an extended warranty ($200+).   And to avoid being (charged) for a 
service call (Uhm... $49 while under warranty), they suggested I look 
into the Knowledge-base on Apples site and it gave me instructions to 
reset the power management unit.  It appeared to be working O.K. in OSX 
afterwards, but tonight I booted into YDL 3.0 and within about 30 
minutes went from a battery of ~85% to 0% and it shut down.  I 
restarted in OSX and it shows 0% battery.

Has anyone been experiencing something similar?