Some photos show up, others do not

I've had gallery up and running for a while now, customizing it and what not, but I've only recently started uploading the actual photos to the gallery. My problem is that while some photos upload fine and can be viewed just as easily, others simply don't show up. Oh they are there, but only as a broken image, in both the thumbnails and original size. Here's a link to one of my album pages so you can see what I'm talking about: http://photo.millersville.edu/gallery/main.php?g2_itemId=15848. You can see there that the first two pages of images are all broken but then on page 3 the photos show up and do so until the last page in the album. The thing is I've deleted and reuploaded these photos countless times and each time it's different photos that won't show up. I know the images are good because they've actually shown up at one point. So I guess my question is, why aren't some photos showing up? Please help, I need to get these photos up ASAP

Here's what I'm running:

Gallery version (not just "2"): 2.3.1 core 1.3.0.1
PHP version (e.g. 5.1.6): 5.3.0 apache2handler
PHPInfo Link (see FAQ):
Webserver (e.g. Apache 1.3.33): Apache/2.2.11 (Unix) mod_ssl/2.2.11 OpenSSL/0.9.8k PHP/5.3.0
Database (e.g. MySql 5.0.32): pdo_sqlite sqlite 3.6.15, lock.system=flock
Activated toolkits (e.g. NetPbm, GD): ArchiveUpload, Exif, Getid3, LinkItemToolkit, Thumbnail, Gd
Operating system (e.g. Linux): Darwin photo.millersville.edu 10.0.0 Darwin Kernel Version 10.0.0: Fri Jul 31 22:46:25 PDT 2009; root:xnu-1456.1.25~1/RELEASE_X86_64 x86_64
Browser (e.g. Firefox 2.0): Mozilla/5.0 (Macintosh; U; PPC Mac OS X 10.4; en-US; rv:1.9.2.6) Gecko/20100625 Firefox/3.6.6