[This has been moved to a separate item DNN-6866: If you put a large file in a secure folder (using FTP) and syncing this folder in the file management module the file is listed with a negative file size. In my example a uploaded a file with 3.770.890.436 Bytes and it is listed with a "Size: -524,076,860.0 B". IMHO, the problem is that the column dbo.Files.Size is of type int and is not able to store values larger than 2,147,483,647. I think the same problem exists for other folder types.]
The second problem and the more important one is, that you cannot download this file in IE (tested with IE10) using a LinkClick.aspx link. When clicking the LinkClick.aspx URL in IE the download processed is stopped immediately after it was started. Downloading the file in Firefox works. Maybe the the LinkClick sends the negative content length and this breaks the download in IE.