Just to back up what Corny has posted:

In the past, changing board levels has caused much heartache. There are quirks in the system! We have seen boards arbitrarily switch to a scribe-only level when someone plays with the board levels. This happened as recent as Goldfest 2009 with one of the tour properties, making the board virtually invisible to the rest of the community. The scribes may be able to read the board, but they cannot change the level. The board originator may change the level back to 0, but the posts do not. They are stuck at the higher level.

I cannot stress this enough, once you have posted on a board that is initially set at patron- or scribe-only level, even if you change your mind and reset the board to 0 afterwards, the reading level of the original posts is stuck at the originally set level. Only the posts made after lowering the board level to 0 will be readable by the general community. And sometimes, even that does not work.

I am warning all, be careful when playing around with board levels. It's a risky business.