I would say the easiest thing to do would be to reset the router and start again if you're not sure what you did. Yes you will need to connect to the router via an ethernet cable.
On my router theres a reset button on the back that you need to push in with a pin that resets the router to factory settings and you'll need to reinput your ISP details and setup your wireless settings again. Maybe quicker than trying to track down what you've done thou.
Something simple that it could be did you change the wireless encryption key? If so you'll need to input the new key into all the machines ditto if you turned on the security features.