I ran into my first huge frustration with Drupal - to be more specific, the problem was with the "AcidFree" module.

One day, and I'm still not sure why, all of the photos disappeared out the albums on this site, while albums on other sites (on this same server) continued to function. This wasn't a huge priority for me; but, I "hacked" at it, on and off, for at least a month.

For anyone facing the same problem, this thread will probably be helpful: http://drupal.org/node/179362 (Post #27)

Of course, I solved things the "hard way"; but, it appears that the steps listed on that thread would've accomplished the same thing.