Last time I meet the problem with long text in comment box what doesn’t accept break-line auto when it get out of the width space. But then I found a pretty nice solution what help me solve the problem very easy with CSS.
word-wrap: break-word; /* IE 5.5-7 */
white-space: -moz-pre-wrap; /* Firefox 1.0-2.0 */
white-space: pre-wrap; /* current browsers */
You can check more detail here http://jsfiddle.net/MCj6s/