Trouble with Track Names

I have had a lot of trouble downloading tack names on iTunes. Sometimes it works, but mostly I get the reply: "CDDB information not available for some of these items". There may be a few CD's which are either mixes or unknown, but it also happens with mainstream, store-bought CDs such as Eric Clapton, U2, Van Morisson. Can anyone help me out? I am using dial-up internet connection on my lap-top.