Since you changed your router, the internal IP address assigned to the slingbox most ikely changed as well.
Reset the slingbox from the button on the back of the unit. You may or maynot have to power cycle the router after doing dso before it becomes usable. After doing so, use the desktop version of slingplayer to rerun the setup assistant. Rerun the internet connection settings options and it will resetup your router correctly for remote usage.