"Unable to fetch post info" problem

I enabled "DEBUG mode" and am getting the following error:

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File: (...)/forum/viewtopic.php
Line: 218

PunBB reported: Unable to fetch post info
Database reported: Can't open file: '805bbr_forum_posts.MYD'. (errno: 145) (Errno: 1016)
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I am pretty dumb when it comes to PHP/mySQL issues, can someone tell me what is going wrong and how I can fix it?

Here is the URL for the forum: http://www.805bbr.com/forum/

Thanks in advance!!!