I've got the same problem I think - I haven't been able to do anything at all with my ArduinoBT. I'm using MacOS Leopard on an Intel iMac with Arduino10.
The ArduinoBT will pair with the iMac, but it shows up as not connected - nothing I do seems to result in it connecting.
I'm usually getting the "ser_open(): can't open device...... Resource busy" error as Radioprotector's post, but sometimes it just hangs completely, and won't even force quit, so I have to physically power the iMac down.
I've spent a day on it now and got nowhere, really disappointing after using the excellent Diecimila especially as it costs so much. I'm on the point of giving up and trying to return the ArduinoBT.