Maybe the battery is dead? I know that they have been around a few years, My battery died on my 30 gig vision:m. Here is a tear-down for you to remove the battery. First off the battery is kinda hard to find I could only find it on this website ( the manufacturer) but it is in what i think is Japanese.
skc. the battery is rated at 1250mAH at 3.7v and is 2.8 x 53 x 85 mm.
step 1.
Set the on/off switch to the hold position. Stick a Flathead screwdriver in and pry out the top closest to the screen. Now the bottom is a bit harder. Insert a flathead screwdriver in the reset
hole and pull up at an angle. It should pop out with a little bit of
force.
You have now exposed 4 screws take them out, and place them aside(someplace safe)
Step 2.
There are two clips in the center on the left and right sides holding
the back plate on. Insert a small knife into the side and gently pry it apart
while working your way down. Pry it up about 2mm. Then do the same to
the other side. You will now be able to pull the back off completely.
You can easily remove the battery.
That should fix your problem.