Post any defects you find in the released or beta versions of the ImageMagick software here. Include the ImageMagick version, OS, and any command-line required to reproduce the problem. Got a patch for a bug? Post it here.
We successfully converted/identified/displayed doesntwork.tif.gz with ImageMagick 6.3.0-5. Give it a try. If it fails for you, let us know and we investigate further.