I think I have the same exact issue as these guys [https://community.sling.com/thread/27896].
My iPhone4S has the $14.99 slingbox app downloaded on it. And I'm currently at home sitting upstairs near my ISP provided wireless router...with my iPhone in one hand (repeatedly failing connect), and on my laptop wirelessly connected to my home's wireless network (33.6MbpsDown/5.7MbpsUp)...as I use it to simultaneously type up this question.
Anyhow, my iPhone is currently connected to my Slingbox's wireless network [named Slingbox_F87D...and it repeatedly says "Connecting to slingbox" for about 2mins, and then ends with "The Slingbox connection failed. Please connect your device back to your home router and try again. [code: W-101]". And when I choose "Try Again" it repeats the cycle and gives me the same error message...repeatedly.
My Slingbox is the M1 model and it's downstairs in the living room. My iPhone is showing 2 of a total 3 bars of connectivity when sitting here upstairs. The SlingboxM1's downstairs location...is perhaps 40-50ft of actual distance
through newly stick-built/non-brick construction [nothing fancy was used in building my home]. Furthermore, I also used
this same $14.99 Slingbox App on my wife's iPhone5S---only downloading it on my iPhone4S days later [after getting the same errors on her iPhone5S]. I also upgraded my ISP's internet service from a 20Down/2Up to a faster 30Down/5Up option...as to make sure my Upload was adequate. Any clue as to why I'm getting errors?