The dailyindex file should be recreated each time a new post is made. If it's not being created, and the index worked fine, then your board has some weird issues. I'm going to ask you to use the support ticket system for further support for this issue. Infopop will need to examine your UBB.

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Charles Capps, Moderator, Post-Install Troubleshooting
PLEASE NOTE: Due to time limitations, I do not provide UBB support via email.