It happens when I try to refresh my brushes. I don't know why though, I've never had it before. Any help would be appreciated.
Yes, but I only use one of them, and very rarely use the separate Admin one, as the account I use is Admin too.
(Just taking a stab in the dark here, I've never had the error and I couldn't find much on it) Go into the Gimp Preferences window. Under the Folders dropdown, go to Brushes. Is your folder listed there? Is Writable checked?