have you checked if you're on mute: a la this post
http://www.saberforum.com/index.php?topic=44462.msg755279#new1) change font bank by holding AV button and stabbing, then rotating to get to another sound bank... you might've been set to mute for some reason
2) turn up the volume by holding AV button and doing two rapid flash-on-clashes, then you can point the saber up to turn up the volume, or down to lower the volume.
edit 1: Oh, and if you haven't tried it yet, recharge the Li_Ion batteries and make sure they're topped up. you said 'fresh batteries', hopefully you're not talking about regular AA's.
edit 2: if you can connect to UltraLauncher, go to "Diamond Controller", then click on the "diagnose" button.... good luck.