We understand the quality issues that you are experiencing with the new Slingbox. It's necessary to determine first if this is being caused by the Slingbox itself or the networks requirements; the Slingbox PRO-HD needs more bandwidth, that could be the issue why the old model works. We need to get more information about the issue that you are having; what's the upload/download speed at home? You can use this 3rd party website to check that: Speedtest.net.
You need to confirm that the system meets the minimum requirements for the Slingbox PRO-HD: