It seems that you are having some issues with your SlingLinks since one of the units have stopped working.
In this case, I recommend you to connect the Slingbox to the router and check if the Slingbox shows solid lights. This test will allow you to determine if the issue is related to the Slingbox or not. The following links will provide you with some troubleshooting steps that will help you to fix this issue:
A guide to basic SlingLink and SlingLink TURBO troubleshooting
Hope this helps!