Vostro 1500 - Wireless Router / AP For Network Is Working But Computer Is Not Able To Use

my boss has a vostro 1500 laptop and is constantly losing internet connection. Before losing connection, a little blue world shows up in front of the computer picture in the lower right hand corner and then says *limited access available*, then he can not connect at all. If he disconnects and then reconnects it works for a short period of time and then the cycle begins again. Recently, i was told it was a new router, so we replaced the old router and still having these issues,