Comment 2 for bug 219914

That's really strange. So there's no disk_cache.conf or disk_cache.load in your /etc/apache2/mods-enabled? Did you use the command-line upgrade tool (do-release-upgrade)? I had very little else installed on this machine at the time.

Obviously this is the best kind of bug. The kind we can't reproduce.

In any case I think the disk_cache.conf file should be changed to not actually enable caching. If the user wants caching she'll want to enable it for specific directories, certainly not for the entire server. Would you consider changing the .conf file?