I noticed a rather embarrassing problem on my forum: in some rare cases, some links typed in a post are blocking the topic to display.
For exemple, it happens with the following link:
http://www.archos.com/support/download/software/sources/gen8-gpl-froyo.tgz
When this is entered in a post on an existing topic, it seems to take a little longer than usual to save, then I am getting back to the topic page without any post. I have to manually delete the faulty post in the database to get the topic displaying again.
My server runs latest SP, but I remember seeing this problem on previous SP versions, I just did not take the time to check in details.