It didn't say anything about modrewrite.
What I just did since my last reply though was reinstall zen photo. Now everything is green:
MySQL setup in zp-config.php
MySQL version 5.0.75
Connect to the database chinamas_zenphoto
MySQL SQL mode
MySQL access rights
MySQL show tables found: zp_administrators, zp_admintoalbum, zp_albums, zp_captcha, zp_comments, zp_images, zp_obj_to_tag, zp_options, zp_tags
MySQL field collations
Zenphoto core files
.htaccess file (RewriteEngine is ON)
.htaccess RewriteBase is /
albums folder
cache folder
locale folders
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So everything seems to be alright now. I think the problem occurred last time when I modified the default theme index.php file. Would modifying that file cause that kind of a problem?