svn: Working copy '<filename>' is missing or not locked
Problem: While doing a svn update, you get the following message: “svn: Working copy ‘[filename]’ is missing or not locked”
Cause: The directory that the file [filename] is in needs executable (i.e. list) permission on for the user that issues the command.
Solution: Set the execution permission, e.g. chmod +x [dir_that_contains_that_file]