Hi there, i have an av340 with the same problem. It maybe because the battery contacts inside are not quite touching the battery enough. You need to take the battery out, get a light an take a look inside. Battery may take a bit off shaking to get out. Anyway you should be able to the contacts which the battery touches. You'll need to somehow hook them and pull towards you. Be carefull though. Hope that helps
Ben edwards, September 2010