The members on my server have found a little glitch, they like to call these blocks "Bermuda blocks" because in these areas you cannot place or destroy blocks. This has nothing to do with worldguard, because I have not created any regions in those areas. Usually their just small areas, I was wondering if there was a fix or if anyone else knew about this.
have you (or your users) just tried loggin out and logging back in? I have sometimes had glitches where blocks will reappear, so is this just a glitch, or permanent?
It might be an issue with your map file. Try loading up a new / different map, and see if you have the same issues.