Bug#285290: apache2 content negotiation issue
I'm using etch 4 and I have the same problem.
The thing that Geoff Crompton said about using a different URI didn't work for me.
I haven't tested yet to see if the "/etc/apache2/conf.d/apache2-doc" will work for me because i don't have a previous installation of apache, but there is one thing that did work for me I renamed some files ex. "mv /usr/share/doc/apache2-doc/manual/index.html /usr/share/doc/apache2-doc/manual/index.var", and it works. I did this because I read in the manual that the files that holds the variants are to be name with that extension "var".