I'm using the (x86) version of IE. My understanding is that this is the 32bit version. I've also attempted to disable the Norton's firewall and virus protection and that unfortunately didn't seem to change the behavior. I spoke with Dish Technical support last night and the representative I spoke with had me do a few things like reset the receiver, reset the router, reset the computer, but eventually ended up saying that they were going to have to turn this over to a different department who would have to look at things on their end. I feel like the problem is with a setting in Win7 as you've suggested, not with anything on Dish's end, but I'm just not sure what to change. They told me I just needed to keep trying it each day for a week or so while the tech department looked at the issue and then call back if it still doesn't work.
I don't mind doing that if that's what I need to do, but, if the problem is with a setting in Win7, I'm not sure their efforts will be productive. I'd be happy to try any suggestions that you have. I'm trying to retire my WinXP machine, but won't be able to until I can get this issue resolved with my Win7 system.
I can log in to my Dish Remote Access account successfully on the Win7 system and when I click the "Watch Live TV" option, I see the lights on my VIP722K come on indicating that my computer is communicating with the receiver, but then it just stops after the "Authenticating..." message with the Error code (43). I'd be happy to provide any additional information that you need. Just for additional information, I've tried this through both IE 9 (32-bit) and Firefox 4.