Is rxvt the only terminal emulator you have? If you have others are they working OK? How are you starting the rxvt terminal?
Are you able to run commands? If so what is the output of
Try running this command and see if you are able to start new lines (if Enter doesn't work try Ctrl+J, Ctrl+L and Ctrl+M (that's press-and-hold Ctrl then press the letter)
What happens if you press Ctrl+C ?