A problem about Authentication‏

Hi
I am using bluez on Gentoo and meet a problem recently.
I was trying to connect to a medical device via bluetooth.
(00:11:B1:B3:4E:B4    clock offset: 0x1242    class: 0x001f00). When I
connect it at first, it works. However, if I accidentally shut off the
device manually and reconnect it, I got the failed message like this,

localhost ~ # rfcomm connect 0 00:11:B1:B3:4E:B4 1
Can't connect RFCOMM socket: Permission denied

The message from hcidump is


localhost ~ # hcidump hci0
HCI sniffer - Bluetooth packet analyzer ver 2.0
device: hci0 snap_len: 1028 filter: 0xffffffffffffffff
< HCI Command: Create Connection (0x01|0x0005) plen 13
    bdaddr 00:11:B1:B3:4E:B4 ptype 0xcc18 rswitch 0x01 clkoffset 0x0000
    Packet type: DM1 DM3 DM5 DH1 DH3 DH5

HCI Event: Command Status (0x0f) plen 4

    Create Connection (0x01|0x0005) status 0x00 ncmd 1

HCI Event: Link Key Request (0x17) plen 6

    bdaddr 00:11:B1:B3:4E:B4
< HCI Command: Link Key Request Reply (0x01|0x000b) plen 22
    bdaddr 00:11:B1:B3:4E:B4 key C0451619A2D93536E094FCFFE8DA160E

HCI Event: Command Complete (0x0e) plen 10

    Link Key Request Reply (0x01|0x000b) ncmd 1
    status 0x00 bdaddr 00:11:B1:B3:4E:B4

HCI Event: Connect Complete (0x03) plen 11

    status 0x05 handle 12 bdaddr 00:11:B1:B3:4E:B4 type ACL encrypt 0x00
    Error: Authentication Failure

So I think I should clean up some residues to finish the process of
authentication. But I don't know where they are under linux filesystem
hierarchy. Of course I can delete them through some GUI bluetooth
manager like gnome-bluetooth. But my supervisor expects that I can
write a code to clean them up.

Can anyone help me?

Thanks

Cheng