What do you thinks wrong with my powerbook?

When the laptop is powered by the battery, usually @ around 50% it just dies on the spot.. when I start it up again the clock has re-set..

I presume it's just a duff battery, does anyone else think it's something more sinister?

Could be the battery, could be the logic board. I assume it's ok when connected to a power supply?

Yeh it works fine when the power is connected, however recently it wouldnt work on power.. (well it was intermittent) so Ive ordered a new supply so we'll see if that works and if it does I'll order a new battery

Which PB model? It may not be relevant, but interesting anyway.

How old is the battery, or better yet, how many charge cycles do you have on it?

When did you last calibrate the battery?

It sounds like a weak/old battery on a model that does not have a backup battery to maintain the system settings when the main battery is dead or removed for an extended time. As you've guessed, the power supply could be the culprit, if it's not charging the battery properly.