For a user who doesn't knows the size limits it's hard too understand what's going wrong: If I upload a 5 MB MP4-file I get the following error:

Upload Failure
test.mp4

Exception: No configured storage engine can store this file. See "Configuring File Storage" in the documentation for information on configuring storage engines.

For me that sounds like I need another container format for that file. There is no storage configured for this file extension. But I think it's the file size. If it is please adjust the error message. Cause I am not the admin who has read the "Configuring File Storage"-manual :)