[Bug 21497] New: ElsterFormular 11.1.1: program window disappears, app keeps running in the background

http://bugs.winehq.org/show_bug.cgi?id=21497

Summary: ElsterFormular 11.1.1: program window disappears, app
                    keeps running in the background
           Product: Wine
           Version: 1.1.37
          Platform: x86
               URL: https://www.elster.de/elfo_down1.php
        OS/Version: Linux
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: -unknown
        AssignedTo: [e-mail]
        ReportedBy: [e-mail]

The latest release of ElsterFormular doesn't work on Wine anymore. It is the
official app to submit tax statements to the german administration and can be
downloaded here: https://www.elster.de/elfo_down1.php (topmost entry)

The behaviour is as follows:

The installer runs fine (it also installs Virtual C++ Redistributable 2008)

It doesn't install vcrun6, although it claims to need it (could be fixed with
winetricks, but doesn't change anything about the bug here)

When I start the app with 'wine elfostarter.exe', the main window appears. When
I select a new tax statement, it loads the forms, but when it is done and
should show the input form, the window disappears. That is, the window where
the form would usually be shown appears for a short time, with the form area
empty, then it disappears. The app keeps running in the background, though.

So, when I subsequently run 'wineboot -e', a popup window from ElsterFormular
appears, asking me to save the tax statement data. I can then save it.

When I try to open the saved statement instead of creating a new one, the
behaviour is the same as with a new statement.

btw. ElsterFormular uses Qt4 for the GUI

How to debug this? Which logs would be helpful? There's no crash, so there's no
backtrace :(