It's necessary to confirm if the issue is related with the network or the Slingbox itself. Have you tried a different network?
I recommend that you connect the Slingbox hardwired to the Linksys E3000 and also attach another TV source like a DVD just for testing purposes, confirm that the Slingbox is not located on top of a hot surface like a cable box or satellite receiver. Finally, Reset the Slingbox and then run the Setup Assistant to verify if the issue persists.
Let us know how it works