Weird terminal behavior after installing RVM

Question

I installed RVM and added this line to the end of my .bash_profile:

[[ -s "$HOME/.rvm/scripts/rvm" ]] && source "$HOME/.rvm/scripts/rvm"  # This loads RVM into a shell session.

Now, whenever I enter a command into my terminal I get a [Process Completed] error and my session ends. This error goes away when I remove this line from my .bash_profile:

alias :='cd ..'

Any ideas why?