I was having a lot of problems with game lag and disconnects (being booted back to the login screen), so after reading up on several suggestions, I did the following:
* Updated the firmware in my router, D-Link DIR-601 from 1.01NA to 1.02NA
* Gave each of the two computers on the network (my wife and I both play SK, she on a desktop, myself on a laptop) a static IP, then set up port forwarding for the ports recommended in the tech help sticky, with half going to one address, and half going to the other.