http://bugs.winehq.org/show_bug.cgi?id=24480
--- Comment #2 from Michael Duelli m.duelli@web.de 2010-10-11 06:47:52 CDT --- You are right, a powerpoint process is still running.
It seems to happen mostly (only?) with PPTX files but not with all of them. In such cases, there is a message about a failure closing PowerPoint.