I'm not very technically minded, so not sure if this will help. The following information is copied from the Sony UK website.
http://support.sony-europe.com/dna/faq/faq.aspx?site='&m=PRS-505&f=PA_PRS
1.Verify that the Reader is turned on.
2.Verify that the Reader battery has an adequate charge.
3.Verify that the USB cable is properly and securely connected to the Reader and the computer.
The USB cable should be connected directly to the computer. Connecting the Reader using a USB hub or extension cable is not supported.
4.Verify that the Reader displays the USB connection indicator.
5.Disconnect the Reader from the computer, close the Reader software and restart the computer.
6.With the Reader disconnected from the computer, perfom a hard reset.
7.With the Reader connected to the computer, uninstall and reinstall the Sony Reader USB driver.
8.Install the Reader software on a different computer and connect the Reader.