sometimes my file just freezes in my vi |vim, what happened?

Ctrl-S is probably the culprit; it stops your screen output in most terminals. As Michael mentioned, you can restore your screen to normal by entering Ctrl-Q.

Theoretically, setting stty -ixon should prevent Ctrl-S from freezing your screen, but it's not working on my local Solaris 10 login.

http://stackoverflow.com/questions/3419820/sometimes-my-file-just-freezes-in-my-vi-vim-what-happened