I can't make new folders

[HSakols]

Hello,

I am using Lightroom and Photoshop CC.  Recently, when I try and make a new folder, I get a message that says the folder could not be created on disk.

Also, when I try to create new files using photoshop I get the following message: Could not save as “_A050627-Master.tif” because the file is locked, you do not have necessary access permissions, or another program is using the file. Use the ‘Get Info’ command in the Finder to ensure the file is unlocked and you have permission to access the file. If the problem persists, save the document to a different file or duplicate it in the Finder.

I've checked that my external hard drive permission are set to read and write.  I"m at a lost of what to check next?

Thanks,
Hugh

[HSakols]

I fixed the problem.  I zapped the p ram to reset the permissions.  I also checked to make sure that the permissions were applied to my images folder.  Seems to have done the job.