I recently attended an online seminar called "Creativity Coaching" (sorry, I can't find a link to it), billed as, essentially, a method for overcoming creative blocks -- whether you're a writer, artist, game designer, or some other creative type.
The practical upshot is this: it's easy to be creative when you're passionate about what you do, but it gets harder when the creativity is forced or mandated on a project that you're not particularly excited about. You might come up with dozens of story ideas for a fantasy RPG every day, but that doesn't mean you can churn out a bunch of help text for Career Mode in Madden 2009 with the same gusto.
If you're in a situation where you feel like you have to do a task rather than wanting to do it, you're at risk for becoming creatively blocked. (This is true for students as much as professionals. In both cases you're often asked to do something that feels arbitrary or tedious to you.)
The solution is to find that passion again. Remember the reason why you love your field in the first place, and go do that for a bit. If you're a game designer, spend a weekend making a short game, as in a Game Jam. If you're an artist doing commercial work, do a personal art project on the side. Basically, do something creative for yourself and not for money or a job, on your own time. I realize that if you're in the middle of crunch, this isn't always the easiest thing to do. But perhaps that's just one more reason for companies to avoid crunch in the first place, if they want to keep their people in top creative form.