Thomas,
Everytime you update a fact in the WM, it is matched against all
the rules. An activation is created for all such matching
cases.
In
your example whenever the fact is updated in Rule 2, two activations are
created, one for Rule 1 and one for Rule 2. Rule 2 doesn't get fired
because of no-loop clause.
A
similar senario occurs when the fact is update in Rule1.
You
may avoid looping by not updating the fact in the WM.
Pallav