has it ever worked correctly or have u just installed it ?
if you can try the laptop on a friends router does it do the same ? if so you need to concentrate on the laptop. if it works fine on your friends there may be a problem with your router. has your friend got a laptop does it do the same on your router ?
in my experiance rebouting the router often solves this problem however there are a number of issues could also cause this.
by trying the above establish if its the laptop you need to look at or the router and come back for more advice
good luck alan