400 and 401 errors

We recently set up new rax120 nighthawk router but everytime we use wireless thru the network, everytime u click a link off the page, we get a 401 unauthorized error or a 400 not found error. I can copy the site and paste it into google or safari and get there that way, but the next time i click anything, we have to do it again. If i change my wireless back to the original modem, dont have this problem but it doesnt reach very far (hence, the router). This may be an easy fix but we need to know how!!!! Help! My kids are eating up data on their phones since none of them can stand this on wireless!