I just had the same problem with the Qwest Actiontec Q1000, which is most likely just a slightly different model based on the region of the country we are both located in...
I am going to write these instructions very basic, in the hopes it may be able to help persons other then yourself. Here they are:
1. Login to your router by typing 192.168.0.1 into the address bar of your internet browser (Internet Explorer, Firefox etc.)
2. Click on the advanced setup tab on the top right
3. Click on "applications" under the security option listed in the column on the left hand side of the screen towards the bottom
4. Under option 2 on your screen (2. Select the application category, then the application to forward.) Click on the 'application category' drop down and select 'user created rule'
5. Click on create rule
6. Rule Name: Slingbox
Port Start: 5001
Port End: 5001
Port Map: 5001
Click on apply button
7. click on applications option again (from #3 above)
8. Select Device ----> Manually enter IP address
Enter IP address ----> 192.168.0.254 (IP address based on default slingbox model -> you can get this information from sling setup wizard if different)
9. Application Category -> User Created Rules
Application ---> Slingbox
10. Click on add or apply on step 3 on your router screen
11. If you want to test it, do so in your Slingbox setup assitant setup wizard screen, and then after it passes that test your overall connection from something "off your network" (in other words test it from your mobile phone, or a computer that is not located on the same internet connection as your sling box)
works like a charm on the internet now, including on the iphone.
Hope that helps anyone with this issue. Also, I should add that the first time I did this on the Qwest Actiontec Q1000 router, it did not correctly save my port forwarding settings... So to make sure your port forwarding is setup correctly you want to make sure that it lists the following at the bottom or your router applications page (applications page from #3 above):
Forwarded Applications List:
192.168.0.254 192.168.0.254 Slingbox