I am using Mandranke 10.2, and it worked fine for a certain time. But now, suddenly all the USB devices (webcam, external harddrive, flash drive...) cannot be recognized by the system. If I plug a usb flash drive to the machine, the light on the flash drive was not even on. But everything works just fine in windowsXP. So does anyone have some idea on this problem?
Thank you very much!

Are the proper modules loaded? ehci/ohci/uhci/etc? What does 'lsmod' show? Anything in dmesg that's usb related?

I am kind of new to Linux, so can you explain the modules stuff in details?

The kernel has many loadable modules. Running 'lsmod' shows those currently loaded. Please post the output of 'lsmod' and 'dmesg | grep -i usb'.

The output of "Ismod" is
Module Size Used by
isofs 31512 0
appletalk 30420 2
ax25 55852 2
ipx 24048 2
udf 85540 0
vmnet 24996 12
vmmon 105036 0
cpufreq_ondemand 5244 0
cpufreq_powersave 1376 0
powernow-k8 10852 0
processor 18164 1 powernow-k8
nfsd 210272 9
lockd 59144 2 nfsd
sunrpc 122788 12 nfsd,lockd
raw 6720 6
autofs4 15268 0
md5 3648 1
ipv6 232320 18
rfcomm 33692 0
l2cap 20644 5 rfcomm
bluetooth 41380 4 rfcomm,l2cap
snd-seq-dummy 2596 0
snd-seq-oss 31584 0
snd-seq-midi-event 6208 1 snd-seq-oss
snd-seq 47472 5 snd-seq-dummy,snd-seq-oss,snd-seq-midi-event
snd-seq-device 6796 3 snd-seq-dummy,snd-seq-oss,snd-seq
snd-pcm-oss 49056 0
snd-mixer-oss 17248 2 snd-pcm-oss
snd-intel8x0 29216 2
snd-ac97-codec 75256 1 snd-intel8x0
snd-pcm 80776 3 snd-pcm-oss,snd-intel8x0,snd-ac97-codec
snd-timer 20324 2 snd-seq,snd-pcm
snd-page-alloc 7588 2 snd-intel8x0,snd-pcm
snd 46980 11 snd-seq-oss,snd-seq,snd-seq-device,snd-pcm-oss,snd-mixer-oss,snd-intel8x0,snd-ac97-codec,snd-pcm,snd-timer
soundcore 7104 2 snd
lp 9864 2
parport_pc 31652 1
parport 31624 2 lp,parport_pc
af_packet 16232 2
ip_vs 92096 0
sis900 17668 0
ide-cd 36772 0
ohci1394 31076 0
ieee1394 292152 1 ohci1394
loop 13544 0
ntfs 205368 1
nls_utf8 1600 3
nls_cp437 5376 2
vfat 11200 2
fat 35964 1 vfat
xfs 573912 3
exportfs 4672 2 nfsd,xfs
amd64-agp 9800 0
sis-agp 6052 1
agpgart 28264 2 amd64-agp,sis-agp
ehci-hcd 28648 0
ohci-hcd 19112 0
usbcore 106008 3 ehci-hcd,ohci-hcd
reiserfs 261012 1
sd_mod 15696 8
sata_sis 4160 7
libata 41316 1 sata_sis
scsi_mod 115144 2 sd_mod,libata

and the output of "dmesg | grep -i usb" is
usbcore: registered new driver usbfs
usbcore: registered new driver hub
ohci_hcd: 2004 Nov 08 USB 1.1 'Open' Host Controller (OHCI) Driver (PCI)

Thanks !!

Hrrm, usbcore and the ehci and ohci drivers are loaded. Try plugging in a USB device and see if the output of 'dmesg | grep -i usb' or 'dmesg | tail' shows anything of significance.

The results I just showed were with 2 usb devices plugged in, but I got the same results if I unplugged the usb devices.

"dmesg | grep -i usb"
usbcore: registered new driver usbfs
usbcore: registered new driver hub
ohci_hcd: 2004 Nov 08 USB 1.1 'Open' Host Controller (OHCI) Driver (PCI)

"dmesg | tail"
UDF-fs INFO UDF 0.9.8.1 (2004/29/09) Mounting volume 'LE2005-DVD', timestamp 2005/04/13 05:08 (1ed4)
VFS: busy inodes on changed media.
VFS: busy inodes on changed media.
UDF-fs INFO UDF 0.9.8.1 (2004/29/09) Mounting volume 'LE2005-DVD', timestamp 2005/04/13 05:08 (1ed4)
VFS: busy inodes on changed media.
VFS: busy inodes on changed media.
floppy0: no floppy controllers found
floppy0: no floppy controllers found
VFS: busy inodes on changed media.
VFS: busy inodes on changed media.