Actually I had the Planarize Lines tool docked to the Editor tool bar, and it didn't work. So I removed it and docked it to the COGO tool bar and it still didn't work. What I should have done was to bring in the Advanced Editing tool bar (with the Planarize Lines tool). It works fine from the Advanced Editing tool bar. I guess if I docked the Planarize Lines tool to a different tool bar, it didn't work.
I wouldn't think the where the tool is docked would have anything to do with if/how if functions. Would it?