When I use earphones on my iphone, only the left side works when using slingplayer. I have tried 3 different sets of earphones, all with the same result. The earphones work fine on all other apps on my iphone (itunes, netflix etc), but only the left side works with slingplayer.
One possibility might be the audio cables on your Slingbox. If you have a chance can you make sure the audio cables are connected properly, and switch them out in case the cable went bad? My guess is your Slingbox is only streaming one side of the (stereo) audio.
Ok, tried 2 other sets of cables...same result. I did notice that when I change the audio settings to right channel only on the slingbox from my pc, there is no sound. Any other ideas? I have stereo sound on my pc when I watch the slingbox.