As I mentioned in a previous thread, it is not always possible to prevent these things happening, it is an automated 'attack' and the first we know of it is when it appears. We (the admin/mod team) normally are on (at least one of us) and they are deleted quickly, but today we all had other things to do. This is rare, and we are one down till Tinkerman gets back.
Ultimately CBF will have to move to a new forum style, as we are simply too big for what we have now and there are too many problems such as these automated spam posts, posts locking themselves etc. and there is no known fix for them. When we move, you'll all be complaining at us because the way of posting etc will be slightly different, but we'll talk you through it
I'm sorry I can only administer CBF on a part time basis, if I could do more than 18 hours a day I would