This is a new one for me. I was dumping some databases on a server when I got this:
mysqldump: Error: 'Got error 28 from storage engine' when trying to dump tablespaces
mysqldump: Couldn't execute 'show fields from `xxxxxx`': Got error 28 from storage engine (1030)
Fortunately the fix was easy, just clean the /tmp folder as it was almost full on that particular server.