After upgraded to VirtualBox 1.5.2, the USB function was gone. I am using Ubuntu 7.10 SE right now.
Hereby, I post the solution :
Step 1 :
sudo addgroup usbfs
Write down the dev group id of the usbfs, such as 1002 or 1003.
Step 2 :
sudo gedit /etc/fstab
Add the following line to the end of the “/etc/fstab” file. The example dev group id below is 1002, if it is 1003, replace with it.
none /proc/bus/usb usbfs devgid=1002,devmode=664 0 0
Step 3 :
Add you to the usbfs group.
sudo usermod -G usbfs -a your_account
If you are new to VirtualBox, you should also refer to the following link.