I see that you stated your bitrate has went down with no changes being made to your Internet. There are many different things that could be causing this issue. You stated that this is happening on your PC correct? Is your PC connected via WiFi? If so, how many other things are connected to the WiFi as well? Is your Slingbox up to date? Are you using the SlingPlayer for desktop and if so, are you using the most recent version?
I know that you stated nothing with your Internet has changed, however, I would suggest that you contact your ISP and they should be able to pinpoint what is causing your bitrate to drop and give you some steps to take to get this issue resolved. However, if you need any further assistance or if there is anything I missed, please do not hesitate to reply.
Sling Moderation Team.