If the user who is uploading the file has a to small bandwidth there can appear such a delay. We are working on a better solution.
For the moment the easiest solution is, that all users must leave the room and come back after some time. In general we recommend to test the uploaded presentation before the seminar starts. In this case just the creator/moderator is in the room and her or he must leave the room before the seminar starts.
Posted in: 1) General Questions