Forum display / index will display repeats forums in certain circumstances

[GoogleCodeExporter]

What steps will reproduce the problem?
1. Create a set of forums (one, two, three)
2. Create posts in each
3. Disable at least one of those forums
4. Create a new forum and make its sort order appear in order
5. Go to index and you'll see a repeat of the forum (fid is correct), but last 
post is not right for new and old forums
6. Create a post in the new forum
7. Go to index and note that the disabled forums are now gone and last post is 
correct

What is the expected output? What do you see instead?

Disabled forums not to be shown under any circumstances
Enabled forums to be shown with correct last post even if blank

Original issue reported on code.google.com by [email protected] on 24 Jun 2010 at 4:22