I'm submitting this solution to a problem I was having when I upgraded to vznav4 which was not getting any voice commands. I have a Pearl 8130.
I contacted verizon and they resolved the issue via the following steps:
1) Go to Options:
2) Select Advanced Options
3) Select Applications
4) Select VZ Navigator
5) Menu to "Edit Permissions"
6) Make sure "Connections" & "User Data" are set to Allow
7) Expand (using menu) "Interactions" and make sure all settings are "allow" except set "Browser Filtering" & "Screen Capturing" to "Deny"
8) Power off/on Blackberry and hopefully vz navigator voice can now be heard