bad chafe

hi.
i've recently just done 100km two days in a row and have had to stop in the last 30km and jump in the car due to really bad chafe. I think my seat is causing it. I have a Trek Madone WSD 5.1 road bike and the saddle is just the one that came stocko with it. Short 40-60k rides are ok but anything longer really gives me trouble.

Any ideas/help on saddles etc ?

Thanks :-)

There's lots of information here.

For basics on saddle fitting, try this thread, and this one.

Is there a good chafe?