1. Which operating system are you using? I had the identical problem with the latest beta when I set up a new account & lacked system permissions to write to other partitions. So ... I changed permissions. (mac osx)

How to change permissions will depend upon your operating system.

In windows, you can set permission access for particular areas of your computer. If you're the admin of your computer then I'd be surprised you had this issue unless you were attempting to save to a system folder area or root level of drive.

2. Where are you trying to save your files to?