What must be the Bee Gees' 234th album starts promisingly with the title song (and single). "This is Where I Came In," a conscious attempt at re-creating their streamlined '60s sound, has a rugged, weathered grace. But while their voices are up to it, the material quickly turns south. Watery ballads and unfortunate forays into harder rock and vaudeville pop make you think they should be dancing again. Pleasant surprise: One of the best tracks, ''Man in the Middle,'' is by Maurice!