Corrupted Images

[Bridger Maxwell]

Hey,
  I have been having troubles with a few of my stacks.  At random times
images that I have imported will just show up as a big rectangle of uniform
black and white pixels.  The only resemblance the image keeps is its
original size.  I think they have all been PNG images.  I would use a
different image type, but PNG is the best for transparency.  Has anyone had
this problem before?  It has happenend in both Revolution Dreamcard
2.5.1and Revolution Studio
2.7.

  TTFN
     Bridger