I have just installed 1.6.6.1 on Windows XP. I found that the Help menu options are mostly broken. Nothing happens when I select Introduction, Tutorial, etc. except on the bottom status line it displays the command. I did a full install including MikTeX. It seems that not all the documentation is being installed. I went back to 1.6.5 and things work much better. I had used the German and the Greek mirrors to get my copies of 1.6.6.1.
