I have to do the same thing, and I am on high-speed. I have to let the clip totally load - or it keeps stopping all the way through - and it is SUCH a nuisance!!
Checking my progress....I opened the link at approx 11:49 AM (CST) and at 12:04 I had 57 seconds of the 4 minute 57 seconds video downloaded. I'm now at the 2:31 mark, and I think the time is approx 12:26 PM. I still have over 2 minutes to go. :(