IPAQ 614 Which bluetooth headset?

Help needed please - I have an Ipaq 614c that in general serves it's purpose as being my phone, PDA, and satnav. The problem is bluetooth headsets when using the phone - with the Jabra BT250v that worked fine with my mobile phone I can hear perfectly well but the microphone doesn't work at all, I have tried Plantronics and Motorola HS810 headsets and each case the microphones work but I can barely hear anything. I've tried the HP forum and bluetooth audio seems to be an unresolved issue with the IPAQ 614, I've also installed a registry editor and tried a couple of recommended tweaks but these had no effect. Any guaranteed tweaks or working headset recommendations would be appreciated.