I hava a client who has recently installed Security DVRs on a few of his properties that are several hundred miles apart. One location has SBS 2003 Premium with ISA 2004 installed. The SBS server has 2 nics, one for WAN and one for LAN. When trying to access one of the remote DVRs from a client PC on the SBS domain via IE7 the username and password prompt for the DVR pops up, accepts the credentials, starts loading the familiar java logo where the video should be and then, where the video should be, it's just a blank white square. I have set ISA to allow all outgoing traffic, and even some incoming ports. Other than that I'm not sure what other settings I may have missed. I have been able to successfully connect and view video from other networks, with and without SBS domains with no problem. The only thing I see different at this location is ISA.
The model of the DVR is ARM RDVR8A160G.