When you use, say, a laptop computer in the room where your Slingbox is located and connect it (via Ethernet or wireless) to the same router and cable modem that are providing the Internet service for your Slingbox, what UPLOAD speed is reported when you visit the website www.speakeasy.net/speedtest and choose a test site that is close to your Slingbox location?
It might be that the upload speeds at your site have degraded in the past 3 months. It is also possible that your Internet Service Provider at the Slingbox has invoked a streaming limit on your network.
I am raising these points because the stuttering, freezing, then disconnection are all symptoms of low upload speeds from the Slingbox to the internet.
And I think there could be another possibility of heat buildup around the Slingbox -- I have mine sitting on "stilts" to increase the distance between the bottom of the Slingbox and the hardwood floor beneath it, to improve air circulation.