Even if you do all of that, there may still be some apps that you can't download. Samsung, for some reason, put a smaller download cap on these phones than the Android Market's cap. A single app download can't be more than 50MB or you will get the error.
I have never tried to download the WW app, but I would be surprised if it was that large. Usually its games and other heavy graphics apps that need that large of a footprint.
Check and see how many apps you have installed to your phone's memory. As 2acclaim and kmf have suggested, move as many apps as possible to your SD card, and see if that solves the problem for you.