Actually I never tried it with the Creative AC charger. Just a DC cig adapter at 4.5V and a LM7805 homemade power supply. I too have to charge between sets. Fortunately that thing charges like a motha-focka! Just a few minutes of charging really goes a long way.
So I guess there are 3 tests to try, AC charger, battery, and cig adapter.
maybe 4 tests... car charger sharing a batt with the pre, car charger w/seperate batt, internal batt, ac wall power. I've used wall power with line-in a million times and never heard a thing, so I'm 99% sure that is OK. When I heard it recently I thought maybe I just got a bunk car charger not thinking that when I used my last one it was with a ua5 and optical in.
Matt