Here are some candidates, some more arguable than others:

Slavery was destroyed by the steam engine.

World wars are no longer rushed into due to nuclear weapons.

The Pill contributed strongly to equal treatment for women.

The automobile changed sexual mores drastically (whether you view this as a "solved problem" or not).

Poverty itself was solved by technology (yeah, I know that statement will be controversial, but I think it's eminently defensible).

In fact, I think a case could be made that technology is the only thing that has ever solved a social problem in anything like a permanent fashion.