Firefox 3.03, and Win XP Home SP3. On the bookmarklet in the bookmark toolbar. Turns out any right-click on any bookmark in the toolbar crashes firefox, so it is not an EN bookmarklet problem.
Have to second this report. Lost back button funtionality in Firefox 3.03 after using the bookmarklet. Funny, this is the first time its happened. Plus, right clicking on the bookmarklet in the toolbar crashes Firefox entirely.