When uploading files to your account, usually the server will make them readable and writable to you (duh), but there are "group" permissions for your group, and a completely separate set for "everyone else". Sometimes the "everyone else" privileges aren't set correctly.

The webserver usually falls into the "everyone else" group, so it may not have privileges to read the files for you. Somewhere in your interface there is some way to set that. Be sure your pictures are set "RW" for you, and "R" for everyone else. There's got to be a way to edit those settings in your interface. If you have shell access via SSH or telnet, you can execute the command
chmod 644 <filename> in the directory where the file resides.
This will set the bytes that control the privileges to RW- for you (6 or 110 binary), R-- for your group (4 or 100 binary) and R-- for everyone else (4 or 100 binary).

My guess though, is the filenames are in caps, at least the extension, and your pages address them in lowercase. I have that problem all the time. The camera generates lower case filenames but Windows changes the extensions to JPG when it copies them. Thanks, Microsoft! Fortunately with Windows XP and on, if you rename them in Explorer, the change stays.

Hope this helps, and if you knew this stuff, sorry for mentioning it :)

hugs
Carla Ann