perhaps. all depends on what settings you messed with. your router probably has a full-reset setting inside its configuration. if you don't have too many custom settings, you might want to just do a full-reset and start from scratch. fyi, i didn't have to set my DNS addresses inside the router itself. those are set to auto. i only have to worry about manually setting DNS addresses in OSX.

again, your router might not be the problem if your ISP decided to give you new DNS addresses or if they are bogged down with lots of traffic on the existing ones. do give opendns.org a try and see if things speed up for you. also, you can check ping times in terminal by typing "ping" and then the DNS address. that way you can see what kind of speeds you're getting from the DNS servers.