Bluesnarfing is the practice of someone partnering with a Bluetooth enabled device without the device's owner being aware. The attacker can read, modify and copy a phone's address book and calendar without leaving a trace of evidence.
Many companies have Bluetooth devices that are vulnerable to such and attack and Nokia has obviously realized the security hole in their phones. Apparently, the Nokia 6310, 6310i, 8910 and 8910i models are at greatest risk.
According to Nokia, a bluesnarfing attack on their phones is only possible if the phone is in 'visible mode' where it is set to actively search for other Bluetooth devices.
Nokia will not be releasing a fix for the devices because the attacks are limited to a few models. The company says you can place your phone in invisible mode to avoid these kinds of attacks.