I use Python 3.1 inside Windows XP and when I try to use more than one module at the same time, the Python shell restarts. What can I do?

This is my module benutzer.py:

```
class Benutzer(object):
    def __init__(self,benutzer):
        self.name =  benutzer
        self.email = None

    def setzeEmail(self, adresse):
        self.email = adresse

```

When I do "Run Module" inside IDLE, the shell says RESTART.