#65 crystal.py causes Segfault on Solaris

[Jonathan Brandmeyer]

Submitted by: "cedric koch-hofer"
<ckochhof@ensisun.imag.fr>
Platorm: Solaris 9, python2.2
After running the crystal.py demo past the benchmark
section, the following errors occur:
> Visual-2003-03-15
> 2.6 sec for 100 steps with 3 on a side
> Traceback (most recent call last):
> File "crystal.py", line 133, in ?
> F = F+norm(r)*(mag(r)-L)
> TypeError: Cannot subtract vector - float
> Segmentation fault