Thank you for posting in our answers forum! I'm sorry to hear you are having issues when connecting to the Slingbox from your iPAd via WiFi. You do have sufficient download speed. However, it is the upload speed that is important when connecting to the Slingbox. I understand you cannot use WiFi after closing out of the SlingPlayer application. Could you reboot the iPad and go to the speedtest application and check the upload speed. A link below will tell you the minimum requirements for upload speed when connecting via iPad. Also, I would try uninstalling and reinstalling the application if it is causing this issue to your iPad when closing out of the application. You will not have to pay for the application again as long as you are logged into the same iTunes account you were logged in to when you purchased the application.
Hope this helps!
The Sling Moderation Team