It should be pretty straight forward on CentOS 5.10. Nice to know what OS, but now one more question: is this remotely hosted on a VPS or is it a shared hosting thang or ? Do you have ssh command line access?
Really could be a browser time out issue.
Have you tried installing via command line?
After creating non-populated moodle25/6 DB (character set utf8 collate utf8_general_ci), manually creating a /var/www/[moodle25/6data?] directory and setting ownership/permissions to apache:apache for that directory, try the install from command line.
cd /var/www/html/moodle25/admin/cli/
php install.php
That will begin installation in the interactive mode. You will be prompted for giving values ... the same items one sees in the web based forms.
'spirit of sharing', Ken