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Pairing unsuccessful, with Tom Tom Live 820, or anything which has bluetooth including this imac.
What are you trying to accomplish with Bluetooth? File Transfer Protocol is not supported.
Bluetooth is supported for handsfree telephone devices/headsets, stereo speakers/headsets, some keyboards, some peer-to-peer apps from the app store, and internet tehtering where provided by the carrier.
Otherwise it will not connect to any phone/device/computer.