I have no issues mounting a usb stick
You first of all have to ensure you have guest additions installed, you will need the root password for this, I cannot help you obtain this if it is something you have forgotten. My only suggestion in this case would be re-install ubuntu. For help with this go to the ubuntu forums.
http://ubuntuforums.org/
Once that issue has been resolved, you install guest additions by first of all starting your virtual machine (VM), once loaded, you first of all press the CTRL host key to exit the window and in the bottom right hand corner of the VM screen, you should see a cdrom icon. If you then right click on this icon you should see an option called "CD/DVD Rom Image...". Click on this option and you will be presented with a list of cdrom images you have made available to Virtualbox, if guest additions is not in the list you will have to add it manually. Click on the guest additions iso and then click select.
now go to a terminal window and type
you should see a file called VBoxLinuxAdditions-x86.run or VBoxLinuxAdditions-amd64.run
x86 for 32-bit OS and amd64 for 63-bit OS
Type in this code selecting the filename appropriate to the OS you are using.
Code: Select all
sudo sh ./VBoxLinuxAdditions-x86.run] 32-Bit OS
sudo sh ./VBoxLinuxAdditions-amd64.run 64-Bit OS
Once this is installed, re-start your VM
Once restarted, plug in your USB stick and your Host OS will pick it up, the as you did for mounting the guest additions iso do the same for your usb stick. Right clcik on the USB icon in the bottom right of your VM window, then left click on the USB stick in the list, it may say generic something or other but it will be the one.