http://bugs.winehq.org/show_bug.cgi?id=30832
--- Comment #1 from wineatic test051102@hotmail.com 2012-06-03 12:32:22 CDT --- I just found out a workaround:
(1) After starting the conversion a dialog appears. (2) Disable the option to embed the ICC-profile. (3) The conversion starts as expected.
I don't know what this option is used for. I convert my raw files to 16-bit .tif files which can then be optimized using other software (like RawTherapee). When it comes to removing any optical artifacts from .cr2 files, Canon's DPP is the only choice. It is able to do that based on the actual lens that was used to shoot the pic.