Hi sbidaho. It appears that your download and upload speed should be sufficient for pulling streaming media.
However, your ping times are really "through the roof" relatively speaking. For reference, my ping time is around 50ms at the same site.
I notice that your internet provider is a wireless broadband provider. They can say it is working well all they want but it appears you are having very slow response time somewhere on their network.
Try this link:
http://myspeed.visualware.com/voip/
It will do a VoIP speedtest that gives you much more "useful" detail about your connection quality. When the test is done it will take you to the "summary" screen showing you a basic overview of your connection's quality with red, yellow, green indicators. You need to click "Click here for detailed analysis" to get the specific numbers.
You are very interested in jitter and upstream/downstream packet loss as well as roundtrip time. A quality internet connection will have 0% packet loss, and almost no jitter. I suspect you'll find that your connection is dropping a ton of packets or they are discarded for being out of order. For a reference, my results are 47ms roundtrip time, upstream jitter .2ms, downstream jitter 3.8ms, packet loss upstream/downstream 0%, discarded packets 0%, packet order 100%.
This type of test utilizes protocols which are more similar to what streaming media uses. Therefore packet order, packet discards, packet loss, and packet jitter are very important determinations of how good of a quality of stream you are going to get. If you don't have this quality than voice over IP calls would be choppy and intermittent much like your media streams are. From my research packet jitter is the largest determining factor in a quality media stream utilizing the most popular streaming media protocol.
http://www.rankingtoday.com/net/videoip-test.php
My tests here show a much worse jitter time of around 80ms and still 0% packet discards for your reference. My video streams work fine at this rating.
Good luck getting your ISP to actually do anything about the bad numbers. They think that if the connection is on and you can browse the internet then their job is done.
EDIT: You are only getting half the rated speed of your connection by the way. I'm not sure if the 2Mbs down, 768KBps up is a guaranteed rate, or just an "up to this rate" plan. Most providers tell you that you can get "up to" 1.5Mbps, or 3.0MBps, etc..