Fresh install of QGIS 2.12.3-1 through OsGeo4W64 on a Win7-x64 machine:
When I try to start QGIS through the start menu, through OsGeo4w/bin/qgis.bat or the OsGeo4W Shell with the command
qgis I get the same behaviour:
The splash screen appears and just after "Setting up GUI" it closes. No error message appears. Besides QGIS (and its automatic dependencies) no other package was installed through the OsGeo4W setup tool.
Any ideas if it is missing a dependency or how I could troubleshoot this issue with no present error message?