I too have the same exact problem... I have a Verizon Westell 7500 and a Verizon Droid 2 with the Sling Mobile app and while I can view slingplayer on my pc and laptop at home on my own network, I am not able to view it on my 3g Droid 2 or my laptop when I am outside my home.
According to the "Sling Media Support" page for my slingbox, I'm apparently all set-up for internet viewing and port 5001 is open and forwarding yet I get nothing when I leave my home.
I'm guessing there is some firewall or barrier here because I can view Sling Mobile when I have the WiFi going here at home but anywhere else? Nada for the sling mobile.
A google search of this seems to indicate that this is a widespread problem with people who have verizon's westell 7500 router but there are no answers to be found as to how to correct the problem... hopefully someone out there can help! It would be greatly appreciated.
Sorry cpeek24 for taking so long to respond. My problem was resolved. I called the contact number from slingbox.com. The problem was with the MTU settings within the router but I dont remember what it was changed too. I remember someone on the forums talking about the MTU settings and how they help him resolve the same problem. Just do a search and youll find it. Also know if you going to call them for assistance, make sure you within 90 days of when you bought or registered your slingbox. I think they may charge you for help if its past that time.I hope this helps. If you need my help just let me know.