Do not have permission?

I'm logged in as admin, but for some reason sometimes when I try to copy files to my external, or delete something off of either the external or the MBP's HD, I get the error message "You do not have sufficient permission to do that, contact your system admin blah blah blah". But...I AM the admin. Seems random, haven't been able to narrow it down so far. Most recently, downloaded Symantec and ran a full system scan, and half the first files it scanned said "Not fully scanned, did not have permission to open the file." Any thoughts?

you probably just need to use Disk Utility to run a Repair permissions on your internal disk.

If the external is Mac formatted you should be able to check Igonore permissions on this Drive if you get info on that drive

Ntfs?

Is your disk drive formatted as NTFS? if so get the Paragon utility NTFS for MAC OSX. and you should be good to go.

I would think that in the 7.5 years since the OP opened this thread the solution was found.