resuming from standby problem slowing down internet speed

Hi, i have windows xp and when i start my notebook inspiron e 1505 and i start browsing the internet , the speed is fast but when i go to standby and then resume from standby and i start browsing on firefox or ie 7, the browsing speed becomes slower..If i log off and then back on it will become faster again but i dont want to have to do that every time..How do i fix this and why is this happening ?

please help..