No Voices audio on Start25

No Voices audio on Start25
Device Type : START25
Serial Number : XD****J*****
Current App : 9.541.3145439.2
Current Bootloader : 5.5274
Current Map : Benelux v1100.11657
Operating system : Windows 7 Ultimate

I am having problems with the installed voices on the Start 25.
The startup sound is present but when I select a (Dutch) voice in the menu and want to test it nothing happens.
The volume is set to half way of the bar.

Thanks for the suggestions.
Greetzzz Ruud

Hi, if is not software then speaker or power amplifier.