Not completing uploads on Course Manager

I have assigned my Apple ID account for Course Manager ( not yet approved ) and have tried to upload iBooks or PDF file. But the horisontal indicator bar for the progress of "Upload" always stops at the end of the bar; like "1.5MB of 1.5MB" and awaiting for several minutes until cancelling the upload. Still I can put web link "http://..." by clicking "Add Material"->"Enter a Web Link".

Would you mind if I ask the way of troubleshooting?

MacBook (late-2009), Mac OS X 10.7.5, Safari

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Satoru