Background:

I use my Mac for web development, running copies of web sites locally. I recently installed the Snow Leopard update, which to all intents and purposes seems to have gone fine, except...

What's not working?

Web-sharing; more specifically I can't turn it on via preferences. The preference pane just hangs when I try to.

So Apache doesn't start on reboot. I can start Apache by hand, but I don't know enough to either setup apache to start with the computer, or to properly fix web sharing.

Further details

My Apache error log shows nothing on when the system boots up (as I would expect).

This is the error message when I try to start web sharing from the sharing preference pane.

28/09/2009 10:58:05 System Preferences[834]	setInetDServiceEnabled failed with 1 for org.apache.httpd

Here's the messages given when I start apache from the command line.

[Mon Sep 28 10:35:53 2009] [warn] Init: Session Cache is not configured [hint: SSLSessionCache]
[Mon Sep 28 10:35:54 2009] [warn] mod_bonjour: Skipping user 'sams' - index file /Users/sams/Sites/index.html has zero length.
[Mon Sep 28 10:35:54 2009] [notice] Digest: generating secret for digest authentication ...
[Mon Sep 28 10:35:54 2009] [notice] Digest: done
[Mon Sep 28 10:35:54 2009] [notice] Apache/2.2.11 (Unix) mod_ssl/2.2.11 OpenSSL/0.9.8k DAV/2 PHP/5.3.0 Phusion_Passenger/2.2.5 configured -- resuming normal operations

Please let me know if you need any further details on this.

Any help would be greatly appreciated.

UPDATE

I have added an answer of my own below - I was able to solve it thanks to being pointed in the right direction by the comments below, so thanks very much. But I'm still not totally clear as to what caused the problem or how my solution addressed it, so I'm leaving the question open for now.