MacVim

When trying to use netrw (:E), you may get this message. This is most likely because the swap/temporary directory has been changed from the default and does not exist.

If your .vimrc file contained this:

" keep from polluting your folders with .swp (swap) files during editing
if has("unix")
	set dir=~/tmp
elseif has("win32")
	set dir=c:\\temp
endif

…you would need to make sure that ~/tmp exists. This same problem would also cause “Unable to open swap file …” errors when trying to edit any file.