Thank you for alerting me to this problem.
Initially, I could not reproduce the problem, and chose to ignore it. However, it is clear to me now that some images have not been appearing in Internet Explorer (the browser which has long been the bane of a developer’s existence).
It was a simple HTML problem. To make my blogging more efficient, I’ve been using this WordPress plugin to spit out image tags with blank attributes, which I sometimes fill in, and sometimes don’t. IE, because Microsoft is so #$!@ special, interprets a blank width as zero rather than defaulting to the image size.
Curious visitors can read more about this quirk here.
I’ve looked through all my posts and removed the empty width attributes. The earliest one was all the way back here. Sorry for the inconvenience.