Original file displayed instead of ImageCached version

I've set up a view listing nodes corresponding to users' profiles- you can see it for yourself at http://mahilab.rice.edu/people . I've configured the picture field to display the "user_pic" imagecache preset, which should be an 80x80px version of users' profile pictures. However, you can clearly see that the View is pointing to and serving the original file (i.e. sites/default/files/pictures/picture-8.jpg) rather than the imagecached version (i.e. sites/default/files/imagecache/user_pic/pictures/picture-8.jpg). If you visit the imagecached version directly, you can see that it is being generated just fine.

Oddly, this view has served me very well for a year or more now- it's only today that I noticed this bizarre behavior, so I figure something must have changed, either with my server configuration or with the installed modules. Unfortunately I haven't checked on this page in a while before today, so it's possible this problem has been going on for a while unnoticed. I've tried clearing all caches, including APC and memcached, and there are no errors associated with retrieving or editing the View.