I took a quick look at the usb modules I have loaded. Are you missing any? (note: some listed are not usb devices or not used for storage)
Code:
lsmod | grep usb
usbhid 69792 0
usb_storage 105536 2
scsi_mod 173744 6 st,sr_mod,sbp2,sg,sd_mod,usb_storage
usbcore 163368 5 usbhid,usb_storage,ehci_hcd,ohci_hcd
ide_core 174720 4 usb_storage,ide_cd,amd74xx,ide_disk
Open up the konsole and enter: sudo tail -f /var/log/messsages
Then reinsert a usb drive. Is the device assigned. Is an error indicated?
What filesystem is supposed to be on the devices. You could try using fsck to repair the filesystems if they are truly damaged. Could you have previously removed the devices before the cache was written to them?