That routinely happens to me too -- finding solutions in the morning of the next day (revelation typically comes while I am in the shower), after having banged my head at the problem for several days before.
Putting the subconscious to work... I read somewhere that his is how it has to be done -- "stimulate" it hard enough first, then "disconnect" and let it run free-wheeled.
Does anyone have any particular tricks and hints to improve this process?