Sounds like you sucked some air into the steering gear from low fluid (or evil spirits). Iv'e also seen wet PS fluid freeze the ice out -- makes the fluid foam and the pump howl. that was a very cold morning, though, had to jumpstart the old Olds that day.
1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!