Rasputin - 6:51 am on Oct 31, 2012 (gmt 0)
Bit of a long shot discovery but might help someone with images traffic so I'll mention it...
I just found out that my robots.txt is now disallowing /images/ after years of allowing it, although I hadn't changed the file myself - turns out that upgrading a joomla site to 2.5.7 using Admin Tools reinserts the standard Joomla 'disallow images' back into robots.txt without mentioning it. Less than ideal!
So if you have a gallery as part of a joomla site it would be worth checking whether images are still allowed.