Download problem index.html

Hello,

This plugin is awesome. Thanks Lenasterg for your continuous development on this plugin.
I have a problem with this. When I wanted to download file by clicking on the link, the browser downloaded index.html. The HTML file is my landing page for the not-logged-in user. The problem is, the browser only download the HTML file if the uploaded file is docx, xlsx, or pptx. Newer version of ms office. When it is a doc, xls, or ppt, it works well.

The solution is, I must right-click on the link, and choose “Save link as”. It works well on every link.
Could you guys help me with this?

Thanks!

Buddypress 1.8
WP 3.7.1

http://wordpress.org/plugins/bp-group-documents/