Without seeing your files I wouldn't be sure. Did you change anything in reference to these planes (sound or texture file editing, etc.)?
Open one of your good files in a minimized window; open the folders to the errant planes and compare them to the good one -- and, for heavean's sake (and more particularly your's), don't change anything in the good one in the process. Make sure all of the files are there, in the correct spot and named properly.