How delete Single Pages?1 user found helpful
should be in the manual!
Go to the sitemap. Check "Show System Pages". Look for "Dashboard" single page and subpages. Look for the single page. Click on it and press delete.
See attached screenshot.
UPDATE: Do not have a file named the same in your theme directory. This will make you waste a lot of time trying to figure out the problem.
I found loads of temp. folders and files on my server, which took up 54 Megabytes?
They were not needed, so deleted offending files and repaired DB.
Then when putting back modified files all was well.
See if that works.