No files accessible after upgrade to CM10
Happy to help. Here's a link to a solution that worked. Notable is the fact that this works for at least two devices that I have troubleshooted, so there's a high probability that this will work for you. While I didn't have the liberty of connecting my device (a Galaxy Nexus GSM) in the USB mode, I did see all my files in the MTP mode after doing everything exactly as it is detailed. All the best!