I am not able to switch the current Ruby version:
➜ ~ rvm list
rvm rubies
ruby-1.9.2-p290 [ x86_64 ]
ruby-1.9.3-p0 [ x86_64 ]
➜ ~ rvm use ruby-1
On a clean install of Ubuntu 12.04 I ran into the same issue. The RVM installer creates or appends to a file called ~/.bash_login the necessary bit of code to avoid the original problem:
[[ -s "$HOME/.rvm/scripts/rvm" ]] && source "$HOME/.rvm/scripts/rvm" # Load RVM into a shell session *as a function*
However this does not seem to get invoked. Adding it to ~/.bashrc resolved the issue for me.