I had a minor issue with an apache problem after a recent Debian upgrade. It seems that a minor bug in the unstable version's postinst causes it to reverse the order of the /etc/apache/modules.conf file. This causes the autoindex module to get loaded after the dir module, which breaks things.
Easiest solution is to cp /etc/apache/modules.conf.old back to /etc/apache/modules.conf, assuming you haven't changed anything. The files should be identical, with the exception of their order being reversed.