Shaw and iTunes

I rent an apartment where Shaw is available and is included in my rent - ergo I do not have my own Shaw account and cannot access their Customer Service. It is approx 16mb download and fine for Netflix, YouTube, and other streaming services. However, I am unable to play an entire movie from/on iTunes. Whether I try and download it for viewing later or stream it I have tried 4 or 5 times and it stops about a third of the way through and will not continue. iTunes have refunded every time but have not answered any questions as to why this is happening? Is it Shaw? Is it iTunes? (2010 MacBook Pro 2.66 GHz Intel Core i7 8 Gig SSD drive) Anyone else have this issue?