I believe your connection issues are seperate from your audio and video issues. The connection issues are a result of Sling Media's problems during the service migration. They moved the services from the Sling Media offices to their parent company's facilities, Echostar. The outcome of that move has resulted in severe reduction in reliability of their Sling Account and Slingbox Locator services.
Many of us has started to use an IP address or URL as a means for negotiation to our Slingbox. This removed the dependancy we had on the Slingbox Locator Service with the Sling ID. In order to by the problem with Sling Accounts, some have even gone as far as to use Slingplayer Desktop 1.5 which doesn't use Sling Accounts.
As for the problem with the no picture and sound, have you try switching video sources? Perhaps the problem is that your tuned into a video source without audio or video.