Check this thread as well for other issues that may come into play, such as the NB Pro's persistent registry and what appear to be a secondary set of backup batteries soldered to a PCB:
http://www.hpcfactor.com/forums/forums/thread-view.asp?tid=13066&posts=36&start=1
(BTW, I keep forgetting to post a pic of those soldered-in batteries, as requested by cmonex. Hopefully I'll remember tonight when I get home.
)