I don't know if this will be helpful or not. I am on Mac OSX Tiger. I used GraphicConverter to create a pict image in QT format and had no problem using IM to convert it to jpg. Sorry I don't have QT Pro to test.
However, using Preview v3.09 to save to PICT and then using IM to convert to jpg, I get the following error
convert zelda4.pict zelda4_pict.jpg
convert: Improper image header `/var/tmp/magick-OtLYrHQr' @ pict.c/ReadPICTImage/871.
convert -version
Version: ImageMagick 6.5.7-4 2009-11-03 Q16
http://www.imagemagick.orgCopyright: Copyright (C) 1999-2009 ImageMagick Studio LLC
Here are 3 files, first two from GraphicConverter, convert fine with IM. Last one from Preview, does not convert with IM
http://www.fmwconcepts.com/misc_tests/z ... _noweb.pcthttp://www.fmwconcepts.com/misc_tests/z ... qt_web.pcthttp://www.fmwconcepts.com/misc_tests/z ... review.pct