When I refresh my view of the index after this has happened, all the threads that were marked yellow before (unread new post) have turned grey.
It's not the end of the world, but it is a bit annoying.

I also sometimes get "page not found" or other error pages when I want to open a thread. So could it be a connection or bandwidth problem with the server?
Another problem, probably related, probably not: Sometimes when I hit the "submit"-button I only get the preview, the post is not added to the board. This can happen two or three times in a row.
Are there other people having similar problems when posting?