What type of Slingbox and connection are you using? Component, HDMI? Also, have you tried resetting your Slingbox? If not, please do a reset and let me know if the issue persists.
This article walks you through the reset process: How to reset your Slingbox to factory settings
I reset my sling box 500 and the problem still persists. I am connecting via component video.
It is interesting in that if I connect with my iPhone first and switch to standard quality the picture appears. Then I can switch back to high quality and it works fine. And further interesting is that once I connect using the iPhone in this manner my computer access is also fine. But if I connect via computer first I cannot fix the problem, even if I switch quality to minimum.
Sent from my iPhone