Conflict of sync with USB Bluetooth dongle

I learned today that I should not sync my mobile phone Nokia 5300 to two different computer (one Windows XP and one MacOSX machine) using the same USB Bluetooth dongle. Doing so confused the mobile phone and thus the iSync on the Mac will fail simply because the mobile refuse to start the connection. Now I am a little regard that I didn't buy some extra USB blue tooth from Hong Kong where it was cheap.