USM (USB Mass Storage) was replaced by MTP somewhere with, at latest, ICS. Some kernels still may contain for USM, but most won't anymore. So here are your options:

* Check the market for Apps which can enable USM again (I heard mentioned a few who *should* be able doing so, including [AL Mass Storage Manager](https://play.google.com/store/apps/details?id=labs.antu.hw.storage), [USB Mass Storage Watcher](https://play.google.com/store/apps/details?id=com.skidmrk.umswatcher), and [Usb Host Controller](https://play.google.com/store/apps/details?id=hu.sztupy.android.usbhostcontroller) -- but no guarantees whatsoever, as I didn't try any due to lack of ICS devices
* install the mtp packages on Ubuntu (`apt-get install mtp-tools`)