Intermittent hangs in the "newton's method" function.

I have observed a strange behavior with pyephem. Sometimes there can be what appears to be an infinite loop in the newton method.

If you try the following you will see what I mean.

import pyephem
mars = ephem.Mars()
boston = ephem.city('Boston')
boston.date = ephem.Date('2008/5/29 15:59:16')
boston.next_rising(mars)

This seems to fix the problem for me, but it is probably not a permanent solution.

[CODE]
def newton(f, x0, x1):
    """Return an x-value at which the given function reaches zero."""
    TOL = 0.0000001
    ITERLIMIT = 1000
    close_runs = 10
    count = 0
    f0, f1 = f(x0), f(x1)
    while f1 and x1 != x0 and f1 != f0 and close_runs > 0 and count < ITERLIMIT:
        count += 1
        x0, x1 = x1, x1 + (x1 - x0) / (f0/f1 - 1)
        f0, f1 = f1, f(x1)
        if abs(f1-f0) < TOL:
            close_runs -= 1
    return x1
[/CODE]

As you can see it is looping in the newton method in the __init__.py for ephem.