ANSWER:

Ensure the autoread function is disabled. This could cause momentary freezes similar to what you are describing.

You can also put the .swp file in a different directory instead of where the file is being edited. After you open the file in vim but before you make any edits, execute

:set dir=/tmp
:vi

If this works, you can default the .swp file location by adding this to your ~/.vimrc

set dir=/tmp

by uther from http://unix.stackexchange.com/questions/37148