first, thank you for providing this really useful plugin to the community!
Everything was working fine for quite sometime, but suddenly I encounter following problem:
Downloads don't start (e.g. http://www.enex-consult.com/downloads?did=3) , there is no error-message, and no entry in any log-file. All permissions are set to 755, and I am also able to download from the plugin edit-page as well as specifying the external urls (e.g. http://www.enex-consult.com/download/EnEx-Consult+Company+Presentation).