Sometimes.
I have a few characters who's plots were completed who I rarely muse for anymore, maybe your characters are craving some resolution to their own existence?

If you need something to spark your muse, try listening to some music. If you're brave enough, try searching for random bands you could buy at the store (but listen to them on youtube before you decide to buy, you don't want to waste your money) and try to find a band that you can really get into.

If you need one to try, how about Owl City or Neon trees? Or even Thriving Ivory, they're a great band too! Sometimes you can even find Enigma at Wal-mart, which is an excellent band to listen to for inspiration.

Or if you've got a music store where you live and like more darker music, you may like a band like Nightwish, Within Temptation, or Halestorm.

Hope those help *nuzzles*