I got the message, "Photos have read-only access."

I got the message, "Photos have read-only access," when trying to save the metadata into a DNG file. I'm on windows 7, and just upgraded to Lightroom 5. The files in Windows have full write and read ability. What am I doing wrong? Or what box do I need to check or uncheck to be able to save my metadata into the DNG files. My catalogue is on an internal drive. The actual images are on an external drive.