I got the same problem. I even tried to plug the battery to the second battery charging slot, still couldn't get it back to life. But the Ipaq screen lights on with progress bar progress for about 5 seconds, then dead again. I even doubted the battery was toasted.
I gave it a final shot:
1. Remove the battery, and then put it back.
2. While the screen lights on, within 2 seconds, cold reset the unit by press the hole with stylus and push the power button at top in the same time.
In my case, the progress bar will keep going until I see the tap screen instruction and everything back to normal. But it reminds me that the removable battery is totally discharged. So I put it in cradle and I am able to synch it with my PC. Everything seems o.k. while it sits in the cradle, except the charging light won't turn red.
When I remove it from the cradle, it still lights on, battery shows 99% which is healthy. but when I turned it off, it won't start anymore. I have to repeat the above steps to revive it. Sometimes I have to remove the battery and wait for a while and then put it back, so that the screen can light on to give me chance to cold reset.
Conclusion: Maybe need a new battery. I will check Ebay to get one.
Please post if you have other solutions.