Is Economics an Equilibrium Discipline?

An interesting post on the Street Light Blog, on currency misalignments, suggests an interesting question: is economics an equilibrium discipline? The very idea of a misaligned FX rate suggests that the natural state is an aligned one: perhaps the fundamentals move faster than the markets adjust, so FX is never in equilibrium. Perhaps (in the language of statistical mechanics) the relaxation time is much longer than the average time between forcings. Actually that makes a lot of sense...

Update. Paul Krugman seems to agree, at least in a limited context:

A free-market economy can get trapped for an extended period in a bad equilibrium in which good things are not demanded because they have never been supplied, and are not supplied because not enough people demand them