some commands are suddenly missing

[packets]

I'm trying to install qmail in debian. I'm not a debian guy but its the OS of the server so I have no choice. It needs high version of perl so I'm installing it via .deb but its looking a lot of dependencies. Then I tried to use apt-get. I first command "apt-get update" then "apt-get -f install". It tooks some time before it finish though sometimes I cancel it then run the command again. Suddenly, when I tried to vi some files, nothing happens. Even the less commands are not working. Is there someone could point me how to restore back? Could it be a corrupt file since I sometimes cancel the update?

[MikeTbob]

Try logging all the way out of the terminal and then log back in. I don't know much about Debian but I'm sure there is a "clean" command for apt-get, but you'd have to google that.