Since my head is sometimes harder than a granite block I made some further experiment with my Palm 750 WM6 Registry set and found that the issue is really on the Audiogateway registry.
When VC 1.6 gets itself installed, it modifies the following registry key from:
FROM: (Original Registry without VC1.6)
HKEY_LOCAL_MACHINE\Software\Microsoft\Bluetooth\Au dioGateway:BTAGExtModule = BTAGExt.dll
TO: (with VC1.6 installed)
HKEY_LOCAL_MACHINE\Software\Microsoft\Bluetooth\Au dioGateway:BTAGExtModule
=\Program Files\Voice Command\vcbthag.dll
This modification does not work on my palm 750 .
When I have set this registry back to BTAGExt.dll ( I have used CEregedit to make the replacement) my Jabra BT Headset was able to listen and deliver Voice Commands to the device and viceversa the device was able to deliver messages and notifications to the BT headset.
Only missing element is Music: Music is still played through the Palm speaker, but I am fairly happy to make calls handfree!
Better than nothing. I hope this hint will be helpful to others. Please let me know if this works.
Regards
RC

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Device History: Palm III, Palm V, Palm T3, Motorola V66, Nokia 6230, Nokia 6131, Treo 750.