Yours is a good solution too.
Unfortunately I didn't know that php version was the problem untill I found the solution because they didn't send me any php upgrade comunication.

Now I'm using php 5.1 (via .htaccess) for solving hosting stability problems with my site.

:hi:

I found a solution for my situation in this post http://www.joomlahacks.com/component/option,com_smf/Itemid,94/topic,4589.msg20446#msg20446

My host switched php to 5.2.5 yesterday and this was the reason of all troubles so  I think that localy it's the same if I use that php version.

My site has the same problem, but "recount totals and statistics" and "search and repair" don't fix it, in my situation.
A strange thing is that only registered users can't read threads with more than 1 page while visitors see correctly all the threads.
This is one of the guilty threads http://eccelinux.org/component/option,com_smf/Itemid,26/topic,370.0/