This is probably too simplistic, but...

have you checked your tire pressure, all around?
Low pressure can do very strange things to the handling characteristics of autos.
Wildly mismatched pressures (usually one tire very low) can do the same.

Steve

STOP terrorism - Drive a HYBRID

Vehicles:
350 miles a week ------------ 2006 HCH II, Magnetic Pearl, w/NAVI (born on May 25, 2006)
350 miles a month ---------- 2003 Mazda Tribute ES-V6
350 miles a year (for now) - 1986 Mercedes 560SL