One of our classmates tried to upload photos and has since then lost the ability to view his own or others photos on our site. Any suggestions?

When you say he's lost the ability to view photos, what does that mean exactly? Is he getting a red X instead of seeing the photos? Or can he not access other Classmates' Profiles at all anymore? Is he able to see other photos on the web? Since I'm not sure what's causing this I'd tell him to try this, in this order:

1) Reboot his computer. You'd be amazed how many problems this alone solves.

2) If that doesn't work, have him clear his brower's cookies, shut down browser, open browser back up, and log in again.