I have a nuvi 255w and I used to have voice alerts working (after following instructions on this site). I updated the POIs and I lost the voice.
here's what I know and have tried:
I know it uses .wav files.
I know the name of the .wav has to be the same as the .gpx file
I know you need sox.exe in the right folder to get POI loader to work.
I have tried manual and auto loading thru POI loader.
I have done all of the above and all I get is a beep.