NOTE: MTP is the recommended method of communication. Please refer to this Knowledge Base article, http://www.normsoft.com/kb/idx/0/154/article/ , to ensure that both your system and your device can operate in this mode.
Open the Pocket Tunes menu, go to 'Preferences' and choose 'Copy from PC preferences', confirm that it says MTP in the drop down menu. If it says anything else, select the drop down and change it to MTP, then close Pocket Tunes and reopen it.