Smile, Sonja. Skate, Sonja. Just don't try to act. One of the most popular and best-remembered of the dozen ice musicals the three-time Olympic skater made in Hollywood in the late 1930s and early 40s, THIN ICE casts her as a skating instructor (surprise, surprise) who is romanced by a prince (Power) masquerading as a reporter. Having won the gold medal in ice skating in 1928, 1932 and 1936, the Norwegian Henie drove a hard bargain with 20th Century-Fox, who carefully built a series of bland but genial light entertainments around her. She does have a certain placid charm, her dimples are adorable (if you like that sort of thing) and, though her skating may seem less dazzling to an age used to triple toe loops and double axles, she's still pretty impressive on those blades. Her numbers are lavishly mounted and showcase her admirably, though she's got more competition on dry land opposite the impossibly gorgeous looks of a very young Power. Henie is also surrounded with plenty of contract second bananas, especially rubber-limbed, rubbed-faced Joan Davis. Thin ice, maybe, but reasonably sturdy entertainment, if you keep your expectations modest.