http://bugs.winehq.org/show_bug.cgi?id=9967
--- Comment #3 from Louis Lenders xerox_xerox2000@yahoo.co.uk 2007-10-14 07:17:06 --- You have to start the application with the full path and cd into the directory:
cd ~/.wine/drive_c/Program\ Files/XOP2.1/ wine "C:\Program Files\XOP2.1\xop.exe"
Did you try it like that, and it still fails?