This, along with my wifi connection dying every hour or two (requiring a restart) makes me wish I had never upgraded to Mavericks.
Link to wifi discussion: https://discussions.apple.com/thread/5535320
Link to wifi discussion: https://discussions.apple.com/thread/5535320
I was never able to fix the problem, but it went away after I bought an AirPort Time Capsule, which now serves as my wireless router. It has an extremely limited feature set compared to a real router, but I haven't had connection problems once since implementing it.
It's so intermittent that it's very hard to diagnose, but that's one thing I've noticed.