[galaxy-dev] file upload of local data

Hello galaxy community, yesterday I installed a new Galaxy instance and followed the recommended steps (creating galaxy user account, galaxy mysql database, changes in universe_wsgi.ini, ...). It works fine except that there's an odd behaviour, concerning the file upload from my local file system. When I select a file for upload, the only thing I see is this blue upload arrow and nothing happens, even for files of a few kb. However, when I select the same file again, I gets uploaded instantely. I have do this for every new file. Do you have any suggestions? Thanks Christian