My Camcorder won't power up when you turn it on, what can i do?

It worked for me.

Remove all power (including lithium batteries) for 30 seconds. Reinstall batteries, connect AC adapter and see if camera will reset. If not, it probably needs service.

Well, up until 2 minutes ago, I had the same problem.
If you hear something sliding back and forth in it, and you've tried replacing the battaries etc, then you might be having the same problem.
For mine, the "spring" [the inner support/connector] for one of the batteries got flattened down, probably from dropping in the batteries rather than sliding them in sideways. Because of this, one of the batteries was unable to touch the conductors on both ends. All I had to do was push the spring up until i could hold up the battery.
Unless you really think this is the case, I wouldn't suggest looking into this though, since I had opened mine up when I noticed this and it's the only way to access that. Well, I supposed you hook it with a loop of thread and try to pull it up some that way, but then you can't really be sure which is the problem, or if that even is the problem...

Good luck with your camera ^_^;

I just posted a problem.  The camera made a beep and the power light started flashing.   It wouldn't power up or do anything.  I followed the advice above, unplugged the external battery charger and removed the battery pack.  It works again.  I feel silly that I didn't think of this.  First rule is unplug everything and restart..!  Thanks for the help!!  

Panasonic NV-VX57 Mini DV Digital Camcorder - GIVING E 01 / E 02 AND U 02 error please help