Internet connection freezing?

Hi.My internet connection keeps freezing at random intervals. The icon in the lower right hand side of the screen says there is still an net conection but i can't access any web site etc. My only way round it is to either re-boot the pc of put it in to standy mode for a minute or so.This problem has been with me for a while now but in recent months has started happening a bit more often.Many thanks

John
November 2008