Same here in Holland,
some clients have all the hurry to finish a project,Ask for fast service, use your work to show of to their client, and then wait to pay for 4 months( most clients are not like that here, and can be trusted)
But it is very frustrating, especially when you were in the position to choose the job (the endresult was nice for portfolio)
But hey, next time when I have to choose, i would choose a projecte of that client.
Good luck with it. One suggestion I would give, is call him everyday, email him, keep him busy.