Dick van Dyke is suffering from fatigue and other symptoms of a "yet-to-be-diagnosed neurological condition," his rep says. Earlier this week, van Dyke canceled a New York appearance where he was set to accept an award, and his rep told ETOnline the 87-year-old, who lives in California, has been advised by doctors not to fly. The New York Post notes that van Dyke tweeted about his problems yesterday: "My head bangs every time I lay down. I've had every test come back that I'm perfectly healthy. Anybody got any ideas?" He says he's had the problem for seven years, and has had a number of tests including a CAT scan, MRI, and spinal tap.