Further to Anna's reply, I'm also interested that you have problems downloading. Do you have problems uploading and downloading to other sites? (e.g. uploading images to Facebook? Downloading music files?). My guess is that this has nothing to do with Mahara.
As a test, can you go to this special Moodle page and see if you can upload and download and then report back?
http://moodle-archive.newman.ac.uk/13-14/course/view.php?id=2211
Thanks,
Bob Ridge-Stearn
Head of e-Learning