I have investigated things a little further. I noticed in my list of 'unknown devices' the following item:
067b2303 /org/freedesktop/Hal/devices/usb_device_67b_2303_noserial
So i deleted this device, unplugged the Denon usb->serial cable from the MD, reloaded the router then re inserted the Denon usb->serial cable.
The device was detected as a 'Generic USB to RS232 dongle' and not as the usual 'AVC-A1SRA (RS232)' device.
So obviously sometime in the last couple of weeks when the denon disconnected, it has been subsequently picked up by the PnP engine but as this generic serial device and i have clicked ignore as i didnt have a clue what it was....
The DCERouter.log shows the following trace for the newly detected Generic USB to RS232 dongle device:
08 12/30/10 23:01:41.374 Received Message from 45 (^[[36;1mHAL / BigRoom^[[0m) to General Info Plug-in(4), type 1 id 808 Command:^[[35;1mGet Unused Serial Ports^[[0m, retry none, parameters:$
08 12/30/10 23:01:41.374 Parameter 2(PK_Device): 45 <0x7b7bdb90>
08 12/30/10 23:01:41.374 Parameter 5(Value To Assign): <0x7b7bdb90>
08 12/30/10 23:01:41.869 Received Message from 45 (^[[36;1mHAL / BigRoom^[[0m) to OnScreen Orbiter(43),Nokia N800(58), type 1 id 809 Command:^[[35;1mDisplay Alert^[[0m, retry none, parameter$
08 12/30/10 23:01:41.869 Parameter 9(Text): Running detection script: 99_PLCBUS_1141.sh <0x99ffab90>
08 12/30/10 23:01:41.869 Parameter 70(Tokens): pnp_55703 <0x99ffab90>
08 12/30/10 23:01:41.869 Parameter 182(Timeout): 60 <0x99ffab90>
08 12/30/10 23:01:41.869 Parameter 251(Interruption): 2 <0x99ffab90>
08 12/30/10 23:01:41.870 Received Message from 14 (^[[36;1mPlug And Play Plug-in / Bedroom (Other)^[[0m) to 42 (^[[36;1mApp Server / BigRoom^[[0m), type 1 id 67 Command:^[[35;1mSpawn Applicat$
08 12/30/10 23:01:41.870 Parameter 13(Filename): /usr/pluto/pnp/99_PLCBUS_1141.sh <0x997f9b90>
08 12/30/10 23:01:41.870 Parameter 50(Name): PNP Detection 55703 99_PLCBUS_1141.sh <0x997f9b90>
08 12/30/10 23:01:41.870 Parameter 51(Arguments): 14 55703 99_PLCBUS_1141.sh pci0000:00/0000:00:04.0/usb1/1-2 <0x997f9b90>
08 12/30/10 23:01:41.870 Parameter 94(SendOnFailure): 0 14 1 806 224 55703 13 "99_PLCBUS_1141.sh" 18 FAIL <0x997f9b90>
08 12/30/10 23:01:41.870 Parameter 95(SendOnSuccess): 0 14 1 806 224 55703 13 "99_PLCBUS_1141.sh" 18 OK <0x997f9b90>
08 12/30/10 23:01:41.870 Parameter 115(Show logo): 0 <0x997f9b90>
08 12/30/10 23:01:41.870 Parameter 120(Retransmit): 0 <0x997f9b90>
08 12/30/10 23:01:41.870 Parameter 126(Exclusive): 0 <0x997f9b90>
08 12/30/10 23:01:41.870 Parameter 241(Detach): 0 <0x997f9b90>
08 12/30/10 23:01:41.991 Received Message from 42 (^[[36;1mApp Server / BigRoom^[[0m) to 42 (^[[36;1mApp Server / BigRoom^[[0m), type 1 id 812 Command:^[[35;1mApplication Exited^[[0m, retry n$
08 12/30/10 23:01:41.991 Parameter 227(PID): 867 <0x807c7b90>
08 12/30/10 23:01:41.991 Parameter 228(Exit Code): 99 <0x807c7b90>
08 12/30/10 23:01:41.993 Received Message from 0 (^[[36;1munknown / ^[[0m) to 14 (^[[36;1mPlug And Play Plug-in / Bedroom (Other)^[[0m), type 1 id 806 Command:^[[35;1mPNP Detection Script Fin$
08 12/30/10 23:01:41.993 Parameter 13(Filename): 99_PLCBUS_1141.sh <0x807c7b90>
08 12/30/10 23:01:41.993 Parameter 18(Errors): FAIL <0x807c7b90>
08 12/30/10 23:01:41.993 Parameter 224(PK_PnpQueue): 55703 <0x807c7b90>
08 12/30/10 23:01:41.993 Parameter 242(Comment): App_Server::SendMessageList <0x807c7b90>
05 12/30/10 23:01:42.020 ^[[33;1mPlug_And_Play_Plugin::CMD_PNP_Detection_Script_Finished queue 55703 got FAIL 0 script: 99_PLCBUS_1141.sh (NOW RUNNING 99_PLCBUS_1141.sh). files 1 99_PLCBUS_1$
01 12/30/10 23:01:42.020 ^[[31;1mPlug_And_Play_Plugin::CMD_PNP_Detection_Script_Finished queue 55703 script 99_PLCBUS_1141.sh PK_DHCPDevice 306 **couldn't run script**^[[0m <0x837cdb90>
08 12/30/10 23:01:42.277 Received Message from 16 (^[[36;1mHAL / Bedroom (Other)^[[0m) to General Info Plug-in(4), type 1 id 808 Command:^[[35;1mGet Unused Serial Ports^[[0m, retry none, par$
08 12/30/10 23:01:42.277 Parameter 2(PK_Device): 16 <0x67df0b90>
08 12/30/10 23:01:42.277 Parameter 5(Value To Assign): <0x67df0b90>
Anyone any ideas as to what might be going on ?
thanks