Thanks!
Since you'll be fixing Mime issues in this next release, I'd like to note that the default mime type for AVI videos, video/avi, is not correct.
After commenting out the defective video/avi entry and adding a line
video/x-msvideo avi
AVI videos loaded fine with the default video plugin, and no longer triggered a download.
Some of the other media mime types may be defective; I didn't have any other media files on hand to test with.