DNN 04.04 has brought us many performance improvements and this is a blessing particularly for those operating in a shared hosting environment. One of the enhancements is the integration of compression into the core and having this on by default. Compression is a good way to reduce the traffic of bytes from the server to the client. Basically every response gets stripped of unwanted bits and pieces and what is left is zipped up to further reduce the load time of the page. The process of (de)compression is much faster on modern day computers than the transport times across the net.
There is, however, one but. The compression must not be applied to a download stream. The download stream is a stream of raw bytes of a file being sent to the client computer. In the case of DMX this is what happens when you click 'download' for a file. Consequently the compression must be turned off during a file download. Luckily the download has already been isolated to allow it to be easily identified by compression agents. The DNN compression mechanism uses a configuration file to tell it what to compress and what not. This file is called Compression.Config and is found in the root of your DNN installation. Make sure it include the following path in the excludedPaths section:
DesktopModules/Bring2mind/DMX/Download.aspx
This should fix any download issues when using DMX in a DNN 4.4 installation.