Summary says it all. Having this line in this vimrc causes
errors when using /usr/bin/cvim if /tmp/vim_backup doesn't
exist. Remove this line.
Doesn't cvim simply create the directory if it doesn't exist?
No. It says:
"filename" Cannot create backup file (use ! to override)
fixed in vim 5.3-6 -- I couldn't reproduce the error message, but
having that in the default vimrc is undoutedly wrong