zekovel,
I don't know your network topology. So, I don't know if the following suggestion will help? If there's a server of some sort which can be used to test the speed of file transfers by both, the fast laptop, and the slow PC (TV-wise), try transferring a large (100MB or so) file to/from the server (FTP, Windows copy, whatever). You'll want to transfer a large enough file, that it provides enough granularity for measurement.
What you'd be looking for is, for example, if the PC and the laptop are on the same LAN, accessing the server (where-ever it is in the world), If the time it takes to transfer a file from both the PC and laptop are pretty much the same, then the issue is probably with TV. However, if the laptop transfers the file to/from the server much faster than the test with the PC (mimicking the behavior of the TV sessions), then there's something going on outside of TV. In this way, at least you're on the road to narrowing it down.