I dont know if this will help (and i seem to be getting flamed whenever i offer help recently), but when i used a batter extender on my zaurus, i had to use rechargable AA batteries (4 x 1.2V = 4.8V) to charge the zaurus from the extender which works fine, whereas when i used regular AA batteries (4 x 1.5V = 6V) it wouldn\'t charge/work with the zaurus.
Maybe try rechargeable batteries?