Inversion of Control is a core aspect of any framework (Ralph Johnson discusses it quite nicely on "Components, Frameworks, Patterns" http://st-www.cs.illinois.edu/users/johnson/cs329/2003/frame...).

Main points: two frameworks can be very hard to use together, unless designed to be (both keep trying to keep the control), frameworks are a lot harder to use than library, as they impose their whole world view, and frameworks encourage tight coupling (there are about 3 patterns from Ralph's book with Erich Gama, Richard Helm and John Vlissides that have this kind of problem to solve).