Fixing "FAT bread failed in fat_clusters_flush" without rebooting

[sunhux G]

After finish copying 4GB of logfiles to thumb drive, I issued
"umount /usb"  where /usb is my mount point for the thumb drv

I probably took out the thumb  drv too fast & errors came out &
after that RHES 4.6's USB port won't recognize any USB devices
plugged into it anymore.

That same USB (FAT formatted) 8GB SANdisk thumb drive can
still be recognized on other RHES 4.x boxes & my Windows.

The dmesg error is :
scsi195 (0:0): rejecting I/O to device being removed
scsi195 (0:0): rejecting I/O to device being removed
FAT bread failed in fat_clusters_flush
usb 1-5: new high speed USB device using address 79
scsi196 : SCSI emulation for USB Mass Storage devices

How can I fix this without rebooting the Prod server?
Can we do somethg like :
   service haldaemon restart
or restart something on-the-fly