http://bugs.winehq.org/show_bug.cgi?id=20371
--- Comment #15 from Hans Leidekker hans@meelstraat.net 2009-11-12 03:46:48 --- Created an attachment (id=24690) --> (http://bugs.winehq.org/attachment.cgi?id=24690) msi: Don't crash if an environment string has no value.
Try this patch.