[plt-scheme] mred, bitmaps, and X memory usage/leak

I have an animator widge that displays by first drawing in an off screen 
bitmap, and then reusing the bitmap until the next update. There is only 
one bitmap reachable at any given time (the current bitmap).

After running a number of animation steps (about a 1000), X memory usage 
climbs to over 1GB, even when I explicitly collect-garbage. X memory is 
not released until I kill the process (at which point the memory is 
released).

Any ideas?

-- vyzo