What kind of USB stick are you using? As one who tried MANY there was SO much trouble with anything other than the White Sandisk 4GB, which IS usable but must be fixed using a patch from Sandisk (all of which is in the knowledge base)
http://support.presonus.com/forums)) So, that said, go to your "My Presonus" account, and with an approved Sandisk drive (again see Knowledge base article) install the latest DRIVER FOR YOUR SOFTWARE ***IMPORTANT*** from your account...
http://support.presonus.com/entries/22417039-StudioLive-AI-Mixer-Firmware-Recovery-Factory-Reset
follow these instructions in case of questions.