I have experienced jerkiness that exactly fits the description the OP gave. There are two separate instances of it and they look very similar.
The first is directly related to ABC primetime TV shows and motion compensating frame interpolation common on 120hz TVs and has nothing to do with any Dishnetwork equipent. ABC has started dropping some frames (to time squeeze the show) which messes up the telecine sequencing that the technology needs to detect and sync with. Nothing to do here but turn off that feature on the TV. However, this only applies to some ABC shows filmed in 24fps, usually the ones aired at the 9pm eastern time block.
The second as far as I can tell has to do with a processor limitation in the 722 that I have. I used to have a 622 and never noticed this problem at all. I got the 722 in February and have only recently noticed the problem. However, it's only during sporting events on local OTA where full bitrate of the channel is used for that sports broadcast. The reason I think I've only noticed it recently is that I don't watch a lot of sports except during football season. When not football season, I'll watch something every once in a while but not often enough for me to notice a trend. Anyway, this is what I've taken notice of:
On both my local OTA 1080i stations (NBC and CBS) which are not multicasted, during football games the motion will get jerky and look somewhat like the 'dropping frames' on high motion sequences. Turning on and off the TV does not fix it. Resetting the DVR does not fix it. Changing the channel and then back to the OTA station does not fix it. Changing the DVR ouput from 1080i to 720p does not fix it. The only way to fix it is to change the channel to the satellite version of the same channel and leaving it there which is a compressed version of the same channel. In fact, this does not happen on any satellite channel.
On my local OTA 720p channels it's a little less clear. For one, ABC is multicasted here with 2 SD channels so I'm getting a compressed 720p from ABC. I watch college football on ABC a lot and I'm sure I've never seen the jerkiness here. My 720p Fox, on the other hand is like my 1080i channels in that it is not multicasted. I could almost swear that Fox is one of the first channels I noticed this on and while I can't say I've watched as much football on Fox as the other channels, I can't say that I've seen the jerkiness on Fox since I started keeping track.
What I'm describing here, I have never noticed on anything other than sports.
In any case, it seems to me that MY 722 has a problem handling high bitrate, high motion video. I did search for info on this issue and found an old thread where the OP of that thread had the identical problem to mine but it was so old that I wasn't allowed to post a reply and he never gave a resolution in that thread (might not have been this forum as I searched several am working on memory here). Anyway, anyone else notice anything quite like this?