Ok, might be you can go to the Web Shields expert settings and tick "scan well known browser processes only"....that is if the DVR software communicates with http....
Failing that, disable your shields individually, one at a time (don't forget to turn them back on, though) and try running the DVR software to narrow things down, find what particular part of Avast! might be at fault.
Knowing what particular DVR software you are speaking of might also help.
Lastly, updating to SP3 might help also, thats just a shot in the dark.