Actually, DISH CINEMA is the VOD service that has movies already downloaded onto your HDD via satellite. Dish Cinema is available on channels 1 and 501, and these titles include a few in 1080p and 3D. Dish Cinema rentals should playback with excellent PQ and stability, as you are just playing back the movie as if you had recorded it on the HDD yourself with a DVR timer. Dish Cinema movies are downloaded to your HDD as a file download, not in real time stream and can only be played AFTER the file download is complete, not during the file download.
Perhaps you were referring to Dish ON DEMAND. That is the service via broadband internet (many titles are available only through the BlockBuster package, but BB works the same way). Dish on demand is NOT a live streaming only service like Netflix, Hulu Plus, or Amazon Prime, but a stream to HDD, meaning that the stream is laid down and saved on the HDD for the rental period for playback at any time for an experience just as if you recorded the content your self on the HDD using a DVR timer or a Dish Cinema type experience with the content all laid down on the HDD with no live streaming hiccups. However, one may choose to view the Dish On Demand or BB content while it is streaming to the HDD, as you had attempted.
I've downloaded several offerings via Dish On Demand and BB, and it has been a positive experience with HD looking very good, even while the content was still streaming. I have 30Mbps downstream so the downloads occur rather quickly, but I also used the same service quite a bit when I had 3Mbps downstream DSL, and the quality of PQ during stream or on playback was excellent, depending upon the quality of the source (print of film) and HD looked great. It was the time to download that took forever with 3Mbps downstream DSL, but all downloads were excellent. A download of an HD movie with no other traffic on your network would take several hours with a 3Mbs downstream and if you started to watch during the stream, you could catch up to the end of the stream before it finishes.
It could have been that particular movie you requested that seems to have a problem at the server. Now, that is something I have encountered more thn once on both Dish with its offerings and on TiVo when attempting to download an Amazon Instant Video (Amazon's rental or purchase ONLY service, not the Prime streaming), to be laid down on the TiVo's HDD but I found it was that one title, and all the others I accessed were fine.
It could be the quality of your internet connection or routers or switches in your chain. This is the common culprit, especially if there is other traffic on your network or others attempting to use the internet the same time as you want to download with such a narrow ISP bandwidth. Please don't tell us you are using a wireless connection from the Dish box to your internet
. If so, you may need a more robust wireless connection or save yourself the trouble and just use Ethernet if you can. It is REALLY worth it. Most wireless connections are so unreliable. However, there are those on this board who can provide advice in getting the best possible wireless connection. Those routers and switches either wireless or wired are cheap things and they often are the culprit. You might try tweaking your router's QOS and see if that helps, and AFTER RMA to make things easier, you could invest in a router that automatically gives priority to Video content (those routers a bit more expensive), if you'd rather not mess with tweaking with several QOS settings.
However, if you have confidence in your connections to the internet and your home network, then if this continues with other titles, and you would like to take advantage of the Dish On Demand service, then you may have to RMA box. Perhaps the Hopper Net adapter is defective. You can transfer any recordings to an external HDD and you can backup your timers and other settings using the Wizard feature before you choose to RMA it.
Let us know what happens.