Car Suddenly Hard to Turn Left on 1998 Buick Riviera

I had just purchased the car used, and was driving it back home. I was making a U-Turn and about half-way thru the turn the power steering just quit. Now the vehicle has power steering to the right, but not to the left. Any suggestions would be appreciated.

bad o-ring seal on slave cylinder left hand side, 50 cent part
1 more answer
The fault is most likely with the power steering rack. However, please have the problem diagnosed by a qualified technician before replacing any parts.