I believe this is a fluke and not a chronic problem but my Entourage is getting a new steering mechanism between the steering wheel and the power steering rack. At least, that's how the dealer service person described it. The steering would hit an increase in turning force at about 1/4 to 1/2 turn in either direction and would occasionally lock up for 1-2 sec as if the pump stopped working.
The dealer folks have been very helpful and motivated to fix this since it is a safety item. I should have it back on Monday. RG