Hi,
I am having the same or similar problems with Ubuntu 10.04 LTS (32bit). I have a generiac U3 flash drive of unkown make/chipset.

Here are the system message when I plug it in and some u3-tool output

Jun 11 17:39:19 ZZZ kernel: [   75.976025] usb 2-5: new high speed USB device using ehci_hcd and address 2
Jun 11 17:39:19 ZZZ kernel: [   76.109747] usb 2-5: configuration #1 chosen from 1 choice
Jun 11 17:39:19 ZZZ kernel: [   76.139346] Initializing USB Mass Storage driver...
Jun 11 17:39:19 ZZZ kernel: [   76.139513] scsi8 : SCSI emulation for USB Mass Storage devices
Jun 11 17:39:19 ZZZ kernel: [   76.139634] usbcore: registered new interface driver usb-storage
Jun 11 17:39:19 ZZZ kernel: [   76.139637] USB Mass Storage support registered.
Jun 11 17:39:24 ZZZ kernel: [   81.137439] scsi 8:0:0:0: Direct-Access     CBM      Flash Disk       5.00 PQ: 0 ANSI: 2
Jun 11 17:39:24 ZZZ kernel: [   81.137801] scsi 8:0:0:1: Direct-Access     CBM      Flash Disk       5.00 PQ: 0 ANSI: 2
Jun 11 17:39:24 ZZZ kernel: [   81.138214] sd 8:0:0:0: Attached scsi generic sg5 type 0
Jun 11 17:39:24 ZZZ kernel: [   81.138328] sd 8:0:0:1: Attached scsi generic sg6 type 0
Jun 11 17:39:24 ZZZ kernel: [   81.139795] sd 8:0:0:0: [sdd] 123800 512-byte logical blocks: (63.3 MB/60.4 MiB)
Jun 11 17:39:24 ZZZ kernel: [   81.141872] sd 8:0:0:1: [sde] 907880 512-byte logical blocks: (464 MB/443 MiB)
Jun 11 17:39:24 ZZZ kernel: [   81.143129] sd 8:0:0:0: [sdd] Write Protect is on
Jun 11 17:39:24 ZZZ kernel: [   81.143822] sd 8:0:0:1: [sde] Write Protect is off
Jun 11 17:39:24 ZZZ kernel: [   81.146671]  sdd:
Jun 11 17:39:24 ZZZ kernel: [   81.147168]  sde: sdd1
Jun 11 17:39:24 ZZZ kernel: [   81.148668]  sde1
Jun 11 17:39:24 ZZZ kernel: [   81.154431] sd 8:0:0:0: [sdd] Attached SCSI removable disk
Jun 11 17:39:24 ZZZ kernel: [   81.154917] sd 8:0:0:1: [sde] Attached SCSI removable disk
Jun 11 17:39:25 ZZZ kernel: [   81.669336] EXT4-fs (sde1): mounted filesystem with ordered data mode

username@ZZZ:~$ u3-tool -V
u3-tool 0.3
subsystem: sg

Copyright (C) 2009
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

username@ZZZ:~$ mount
...
/dev/sde1 on /media/New Volume type ext4 (rw,nosuid,nodev,uhelper=udisks)
/dev/sdd1 on /media/DISK_IMG type vfat (ro,nosuid,nodev,uhelper=udisks,uid=1000,gid=1000,shortname=mixed,dmask=0077,utf8=1,flush)

username@ZZZ:~$ sudo u3-tool -i /dev/sdd
Error opening device: Read-only file system

username@ZZZ:~$ sudo u3-tool -i /dev/sde
u3_partition_info() failed: Device reported command failed: status 1

username@ZZZ:~$ sudo u3-tool -D  /dev/sdd
Error opening device: Read-only file system

username@ZZZ:~$ sudo u3-tool -D  /dev/sde
u3_partition_info() failed: Device reported command failed: status 1
u3_data_partition_info() failed: Device reported command failed: status 1
u3_chip_info() failed: Device reported command failed: status 1
u3_read_device_property() failed for property 0x03: Header of property 0x0003 could not be read.
u3_read_device_property() failed for property 0x0C: Header of property 0x000C could not be read.
username@ZZZ:~$ 

Any suggestions?
Thank you,
Tony.