shutdown failed

[Pirat SRIYOTHA]

hi sirs,

my machine is thinkpad r51 with FreeBSD siting.thai-aec.org 6.0-STABLE 
FreeBSD 6.0-STABLE #0: Tue Nov 15 11:38:48 ICT 2005     
root at siting.thai-aec.org:/usr/obj/usr/src/sys/SITING  i386

which is now attached to r51 via usb port as da0.

i can start freebsd from this device but upon shutdown i got errors that say

synchronize cahce failed, status == 0xb, scsi status == 0x0
panic: umass_cam_cb func-code -481711512

and die and i need to power down manually.
here is dmesg for your information

%dmesg
Copyright (c) 1992-2005 The FreeBSD Project.
Copyright (c) 1979, 1980, 1983, 1986, 1988, 1989, 1991, 1992, 1993, 1994
        The Regents of the University of California. All rights reserved.
FreeBSD 6.0-STABLE #0: Tue Nov 15 11:38:48 ICT 2005
    root at siting.thai-aec.org:/usr/obj/usr/src/sys/SITING
Timecounter "i8254" frequency 1193182 Hz quality 0
CPU: Intel(R) Pentium(R) M processor 1.60GHz (1594.83-MHz 686-class CPU)
  Origin = "GenuineIntel"  Id = 0x6d6  Stepping = 6
  
Features=0xafe9f9bf<FPU,VME,DE,PSE,TSC,MSR,MCE,CX8,SEP,MTRR,PGE,MCA,CMOV,PAT,CLFLUSH,DTS,ACPI,MMX,FXSR,SSE,SSE2,SS,TM,PBE>
  Features2=0x180<EST,TM2>
real memory  = 1064173568 (1014 MB)
avail memory = 1032466432 (984 MB)
npx0: [FAST]
npx0: <math processor> on motherboard
npx0: INT 16 interface
acpi0: <IBM TP-1V> on motherboard
acpi_ec0: <Embedded Controller: GPE 0x1c, ECDT> port 0x62,0x66 on acpi0
acpi0: Power Button (fixed)
pci_link0: <ACPI PCI Link LNKA> irq 11 on acpi0
pci_link1: <ACPI PCI Link LNKB> irq 11 on acpi0
pci_link2: <ACPI PCI Link LNKC> irq 11 on acpi0
pci_link3: <ACPI PCI Link LNKD> irq 11 on acpi0
pci_link4: <ACPI PCI Link LNKE> irq 11 on acpi0
pci_link5: <ACPI PCI Link LNKF> irq 11 on acpi0
pci_link6: <ACPI PCI Link LNKG> on acpi0
pci_link7: <ACPI PCI Link LNKH> irq 11 on acpi0
Timecounter "ACPI-fast" frequency 3579545 Hz quality 1000
acpi_timer0: <24-bit timer at 3.579545MHz> port 0x1008-0x100b on acpi0
cpu0: <ACPI CPU> on acpi0
acpi_perf0: <ACPI CPU Frequency Control> on cpu0
acpi_throttle0: <ACPI CPU Throttling> on cpu0
acpi_lid0: <Control Method Lid Switch> on acpi0
acpi_button0: <Sleep Button> on acpi0
pcib0: <ACPI Host-PCI bridge> port 0xcf8-0xcff on acpi0
pci0: <ACPI PCI bus> on pcib0
pci0: <base peripheral> at device 0.1 (no driver attached)
pci0: <base peripheral> at device 0.3 (no driver attached)
agp0: <Intel 82855GME (855GME GMCH) SVGA controller> port 0x1800-0x1807 
mem 0xe0000000-0xe7ffffff,0xd0000000-0xd007ffff irq 11 at device 2.0 on pci0
agp0: detected 8060k stolen memory
agp0: aperture size is 128M
pci0: <display> at device 2.1 (no driver attached)
uhci0: <Intel 82801DB (ICH4) USB controller USB-A> port 0x1820-0x183f 
irq 11 at device 29.0 on pci0
uhci0: [GIANT-LOCKED]
usb0: <Intel 82801DB (ICH4) USB controller USB-A> on uhci0
usb0: USB revision 1.0
uhub0: Intel UHCI root hub, class 9/0, rev 1.00/1.00, addr 1
uhub0: 2 ports with 2 removable, self powered
uhci1: <Intel 82801DB (ICH4) USB controller USB-B> port 0x1840-0x185f 
irq 11 at device 29.1 on pci0
uhci1: [GIANT-LOCKED]
usb1: <Intel 82801DB (ICH4) USB controller USB-B> on uhci1
usb1: USB revision 1.0
uhub1: Intel UHCI root hub, class 9/0, rev 1.00/1.00, addr 1
uhub1: 2 ports with 2 removable, self powered
uhci2: <Intel 82801DB (ICH4) USB controller USB-C> port 0x1860-0x187f 
irq 11 at device 29.2 on pci0
uhci2: [GIANT-LOCKED]
usb2: <Intel 82801DB (ICH4) USB controller USB-C> on uhci2
usb2: USB revision 1.0
uhub2: Intel UHCI root hub, class 9/0, rev 1.00/1.00, addr 1
uhub2: 2 ports with 2 removable, self powered
pci0: <serial bus, USB> at device 29.7 (no driver attached)
pcib1: <ACPI PCI-PCI bridge> at device 30.0 on pci0
pci2: <ACPI PCI bus> on pcib1
cbb0: <TI4510 PCI-CardBus Bridge> mem 0xb0000000-0xb0000fff irq 11 at 
device 0.0 on pci2
cardbus0: <CardBus bus> on cbb0
pccard0: <16-bit PCCard bus> on cbb0
fwohci0: <1394 Open Host Controller Interface> mem 
0xb1000000-0xb10007ff,0xd0210000-0xd0213fff irq 11 at device 0.1 on pci2
fwohci0: OHCI version 1.10 (ROM=0)
fwohci0: No. of Isochronous channels is 4.
fwohci0: EUI64 00:06:1b:03:24:02:b8:fb
fwohci0: Phy 1394a available S400, 2 ports.
fwohci0: Link S400, max_rec 2048 bytes.
firewire0: <IEEE1394(FireWire) bus> on fwohci0
fwe0: <Ethernet over FireWire> on firewire0
if_fwe0: Fake Ethernet address: 02:06:1b:02:b8:fb
fwe0: Ethernet address: 02:06:1b:02:b8:fb
fwe0: if_start running deferred for Giant
sbp0: <SBP-2/SCSI over FireWire> on firewire0
fwohci0: Initiate bus reset
fwohci0: node_id=0xc800ffc0, gen=1, CYCLEMASTER mode
firewire0: 1 nodes, maxhop <= 0, cable IRM = 0 (me)
firewire0: bus manager 0 (me)
em0: <Intel(R) PRO/1000 Network Connection, Version - 2.1.7> port 
0x7000-0x703f mem 0xd0220000-0xd023ffff irq 11 at device 1.0 on pci2
em0: Ethernet address: 00:11:25:b2:23:be
em0:  Speed:N/A  Duplex:N/A
pci2: <network, ethernet> at device 2.0 (no driver attached)
isab0: <PCI-ISA bridge> at device 31.0 on pci0
isa0: <ISA bus> on isab0
atapci0: <Intel ICH4 UDMA100 controller> port 
0x1f0-0x1f7,0x3f6,0x170-0x177,0x376,0x1810-0x181f at device 31.1 on pci0
ata0: <ATA channel 0> on atapci0
ata1: <ATA channel 1> on atapci0
pci0: <serial bus, SMBus> at device 31.3 (no driver attached)
pcm0: <Intel ICH4 (82801DB)> port 0x1c00-0x1cff,0x18c0-0x18ff mem 
0xd0100c00-0xd0100dff,0xd0100800-0xd01008ff irq 11 at device 31.5 on pci0
pcm0: [GIANT-LOCKED]
pcm0: <Analog Devices AD1981B AC97 Codec>
pci0: <simple comms, generic modem> at device 31.6 (no driver attached)
acpi_tz0: <Thermal Zone> on acpi0
atkbdc0: <Keyboard controller (i8042)> port 0x60,0x64 irq 1 on acpi0
atkbd0: <AT Keyboard> irq 1 on atkbdc0
kbd0 at atkbd0
atkbd0: [GIANT-LOCKED]
psm0: <PS/2 Mouse> irq 12 on atkbdc0
psm0: [GIANT-LOCKED]
psm0: model Generic PS/2 mouse, device ID 0
fdc0: <floppy drive controller (FDE)> port 0x3f0-0x3f5,0x3f7 irq 6 drq 2 
on acpi0
fdc0: [FAST]
sio0: configured irq 4 not in bitmap of probed irqs 0
sio0: port may not be enabled
sio0: <16550A-compatible COM port> port 0x3f8-0x3ff irq 4 flags 0x10 on 
acpi0
sio0: type 8250 or not responding
ppc0: <Standard parallel printer port> port 0x3bc-0x3be irq 7 on acpi0
ppc0: Generic chipset (NIBBLE-only) in COMPATIBLE mode
ppbus0: <Parallel port bus> on ppc0
lpt0: <Printer> on ppbus0
lpt0: Interrupt-driven port
ppi0: <Parallel I/O> on ppbus0
plip0: <PLIP network interface> on ppbus0
sio1: configured irq 3 not in bitmap of probed irqs 0
sio1: port may not be enabled
battery0: <ACPI Control Method Battery> on acpi0
acpi_acad0: <AC Adapter> on acpi0
sio1: configured irq 3 not in bitmap of probed irqs 0
sio1: port may not be enabled
pmtimer0 on isa0
orm0: <ISA Option ROMs> at iomem 
0xcd000-0xcdfff,0xce000-0xcefff,0xdc000-0xdffff on isa0
sc0: <System console> at flags 0x100 on isa0
sc0: VGA <16 virtual consoles, flags=0x300>
sio1: configured irq 3 not in bitmap of probed irqs 0
sio1: port may not be enabled
vga0: <Generic ISA VGA> at port 0x3c0-0x3df iomem 0xa0000-0xbffff on isa0
umass0: vendor 0x05e3 USB TO IDE, rev 2.00/0.33, addr 2
Timecounter "TSC" frequency 1594832599 Hz quality 800
Timecounters tick every 1.000 msec
ipfw2 (+ipv6) initialized, divert loadable, rule-based forwarding 
disabled, default to deny, logging unlimited
ad0: 76319MB <IC25N080ATMR04 0 MO4OADEA> at ata0-master UDMA100
acd0: CDRW <HL-DT-STCD-RW/DVD DRIVE GCC-4241N/1.04> at ata1-master UDMA33
da0 at umass-sim0 bus 0 target 0 lun 0
da0: <HTS42404 0M9AT00 0811> Fixed Direct Access SCSI-0 device
da0: 1.000MB/s transfers
da0: 38154MB (78140160 512 byte sectors: 255H 63S/T 4864C)
Trying to mount root from ufs:/dev/da0s2a
%

thanks in advance for any helps and hints and please cc to me too.

with best regards,
psr