When using an Ethernet cord, I have no problems connecting to the internet. Also, my iPhone and my Wii have no problems connecting (wirelessly). However, I can't get any laptops to connect to my wireless. I have tried three different laptops and get the same problem, that it can connect to the network but limited or no connectivity. ATT said there was nothing wrong with my gateway router since my iPhone was working fine, but honestly, I don't have a clue.
More aboutlimited connectivity
Stupid question, but have you tried restarting the modem?
I've had that a few times with my older equipment, a restart will fix it for a bit. A few weeks/days later I'll have to restart again because nothing connects!