For the past few days I have found that if I am not logged in then when I click on some thread links on the home page the following error appears:

A critical error has occurred. Index was out of range. Must be non-negative and less than the size of the collection. Parameter name: index

The error persists even after a page reload. I am using Opera 9.63 (although this looks more like a back end problem).

This issue has been fixed, apologies for any inconvenience.

I'm getting critical errors trying to get to some threads (e.g. http://zfooty.com.au/Forum/tabid/58/forumid/7/threadid/998/scope/posts/threadpage/1/Default.aspx#1064). In case it helps I noticed that this thread is mysteriously absent from the Active Threads list - might be related. 

Thanks for bringing this to our attention, that particular thread has been fixed (http://www.zfooty.com.au/Forum/tabid/58/forumid/17/threadid/906/scope/posts/threadpage/3/Default.aspx#1063). It appears to be a forum error (erroneous values inserted into the database) and it doesn't look like it follows an obvious pattern. I'll look into resolving the issue asap, as well as the email notification problem.

Apologies for the inconvenience all.