My comments vanished after upgrading to from 1.2 to 1.5. Existing comments were not showing and the ability to post comments was not available.
I read this thread http://wordpress.org/support/topic.php?id=23507 and tried to copy over the default comments.php but that had no effect. Comments do work and show when I use the default template.
The thread has a whole lot of different approaches to the problem, some of which I do not understand, involving redirects and roots and such.
Is there, somewhere, a solution to this problem? Or a list of things to try in a specific order?