I've been burned out at various times, although never for more than a month or so. Some things I've done to fix things:
Try a radically different system or genre. Even running the same game in a different way helps.
Play for a while. Truth be told, I'm a really bad player, the same way as I'm a really bad passenger - I like to be doing the driving. So, within a couple of weeks playing in a game, I'm always itching to get back to DMing (no matter how good the DM).
Just relax. There was a point, about last July, where I'd committed to running a fairly intense game, and found that I couldn't bear the thought of spending one more minute creating setting details. Unfortunately, the other DM in the group wasn't in a position to run anything. So, I took a step back, and started running the Shackled City path from Dungeon, in a very old-school "kick-in-the-door" style. The characters are wafer-thin, the setting is no more detailed than its presentation in Dungeon, and we're having a great time. Plus, by the time the PCs were third level, I was busily dreaming up campaigns for the future.
If all else fails, just take a break. Don't DM, and don't play. Don't even watch fantasy films, read fantasy novels, or otherwise immerse yourself in your usual sources. Instead, branch out into other fields for a while. Basically, give your brain a change of diet.