Just wanted to record this before the short-term memory erases...
Running:
Moodle 1.5.1
MySQL 4.1.12
PHP 5.0.4
on Solaris 8
After installing the config.php file, the system would not proceed to the next screen (GPL). Discovered that commenting line 208 in /lib/setup.php - [ini_set('session.save_path', $CFG->dataroot .'/sessions');] fixed the problem. This caused the session information to be stored in the /tmp directory (the PHP default) instead of the dataroot/sessions directory. The sessions files were actually being created but no information written to them. I'm sure this has something to do with file permissions (directory and file owner nobody and 777 permissions) but this is a quick fix to get around it. Hopefully no downsteam repercussions.
Cheers,
Rob