Some images don't display in IE 6 or 7

I have a list of administrative staff on my website that have thumbnails of each staffer linked to a greybox popup of a larger image. I’m experiencing problems getting all of my thumbnail images to display in Internet Explorer 6 and 7. I don’t really care about IE 6, but the problem persists in IE 7. The Greybox popup link does work, but all I see is a red X in a correctly sized empty rectangle. I have set up a proper template for the specific page in question and I’m using <img src="<?php bloginfo('stylesheet_directory'); ?>/images/faculty/thumbs/limJaeSam.jpg" width="75" height="75" title="Lim, Jae-Sam" /> Most of the thumbnails display there are four that don’t: Lim, Jae-sam; Ahn, Kun-soo; Lee, Kyung-hun; and Park, Soo-jin

They all display properly and function properly in all other browsers. But, alas, IE is causing problems.

Please, help.

If this is redundant I’d appreciate it if you could point me to the forum discussion where this problem is addressed and solved.

Thanks.

Here is the link to the page:
https://astudies.sch.ac.kr/home/administrative-staff/