Is there such a thing as an “Oscar curse”?

At this year's Academy Awards, Catherine Zeta-Jones and Renée Zellweger will reunite with the rest of the "Chicago" cast to present an Oscar. Zeta-Jones won an Oscar for 2002's "Chicago," while Zellweger picked one up the following year for "Cold Mountain."

Why, then, have they — and other Oscar winners, especially women — had such a difficult road after their crowning moments?