Pair Plantronics Discovery 975 to iMac?

Hello,

I have been able to pair and connect the above headset device to my iPhone 4; however, while I can get the headset paired to my iMac (for Skype conferencing), the audio doesn't "connect" and I get an error message that audio failed. I have turned off the Bluetooth on the iPhone 4 when attempting to connect to my desktop. Is there a solution for this or am I doing something wrong?

Many thanks.
lsb