iPhone not synching all selected albums

With the iPhone connected to the computer and the music tab selected on the iTunes/iPhone page, "Sync music" is checked and the radio button for "Selected playlists" is selected. In the window containing my playlists, several playlists are checked. If I click on "Apply," only some of the playlists are transferred to the iPhone.

Also, if I uncheck "Sync music," I get a warning that all music will be erased from the iPhone, but that doesn't happen either.

Any suggestions?