2008.04.22 22:30 "RE: [Tiff] warning message: Line length mismatch", by Bob Friesenhahn
The libtiff version is 3.8.2. I also tested with 3.7.1 and it gives the same warning. We do have an our own CCITT Group 4 decompression library. We stopped using it about 1 year ago and started using libtiff because it was not complete and the programmer who wrote it was no longer with us. When I ran it through our own decompression library it decompressed properly.
It is worth giving 3.9.0beta a try since it is less buggy than 3.8.2 even though it has the "beta" suffix.
If you can provide a sample of the problem image then several of us can see if we can reproduce the problem.
GraphicsMagick Maintainer, http://www.GraphicsMagick.org/