I was made aware of an image display problem on another computer. Didn't think much of it as the website worked fine on my pc and also in different browsers.
Had a look at it on this other PC today and discovered that only about 50% of images appear. The rest aren't even replaced with the red X - they just don't seem to exist - even the link info in the source is missing.
The same problem on this PC with IE and Firefox, so it's not likely to be a browser problem.
Checked the links with Xenu and they are all ok. Browsing directly to the URL's of the images also works. I know that this PC displayed things just fine until about a week ago.
The website is pure html, no php / database... Does anyone have an idea what could cause this?