There's a nice article over at About.com.
One painful example (from the above article--go read it if you're blocked on what proper treatment might be in the below case):
Etiology: As a child the patient was probably compelled to stand in a corner because he wrote, in a composition: "Grandma gave me a piece of apple pie, then I had another piece of apple pie and then I had another piece of apple pie."
Symptoms: The patient now writes: "The wife gave me a piece of apple pie, then I obtained another slice of the pastry containing the round fleshy fruit, and then I secured another portion of the all-American dessert." As is evident, monologophobia is usually accompanied by synonymomania.
This came up over at imaginaries.org lately (yesterday, give or take?).
What it brings to mind for me is something I've experienced in my writing: deja-word. I know I've found the right word when I do a quick search and realize I actually haven't yet used it at all. Sometimes, though, I realize I've used the word "slowly" five times in a paragraph, and, er, pray I can fix it in revision.