Now, with this new version of ubuntu, i will post alot about it while I'm trying configurations. I don't want to teach how to install VirtualBox 2.2, because it's a package .deb and is so easy to install it (Download Sun VirtualBox). In this post I want to remember that we should select the option "Enable IO APIC" in "Settings - General - Advanced". (My version of WinXp doesn't work without it). So if you system is not booting, verify this option. Now let's go to enable USB in your Virtual machine.
You have to install "Guest Additions", use the menu "Devices - Install Guest Additions". (Don't forget to mount it on your cd in virtualbox)
After you install it go to console:
$ grep vbox /etc/group
The result is something similar to this: vboxusers:x:gid:user
(If your user is not there, add it "System - Administration - Users and groups")
Edit the file "mountkernfs.sh":
$ sudo pico /etc/init.d/mountkernfs.sh
Go to the end of do_start(), and before the } add this line:
domount usbfs "" /proc/bus/usb usbdevfs -onoexec,nosuid,nodev,devgid=GID,devmode=644
(Replace the GID with your GID)
Save the file, reboot the computer and use your usb in your virtualmachine.
The site that make me try this way is http://www.davidgrant.ca/virtualbox_usb_windows_xp_guest_ubuntu_hardy. This website don't says it works on Ubuntu 9.04 (Jaunty), so i tried and it worked.
I hope this is useful,
PS: You have to select the device you want to use in virtual machine in "Device - USB DEVICES"