According to the size of the file and your internet connection, it can be long to upload your flight track (about  1 to 2 minutes for a 3 hours task on a low upload speed DSL connection).

Firefox users, be aware of problem caused by some extensions (like SessionSaver); flight track submission (upload) is very long or impossible and you should think to deactivate them before uploading (this problem occurs on every web sites where you need to upload a document).

There isn't problem with Internet Explorer.