You can install it on as many computers as you want; however, you're only allowed two concurrent activations, provided that systems are not used concurrently (e.g. a workstation and a laptop). You can deactivate one of the installs, and activate another, if you need access to the software on another computer.
What if a person has Production Studio CS2. Due to a major crach the suite has to be installed again.
AE is greyed out and Adobe cant help to get it working and also told this person he had only two activations left.
I do not know if this applies to PrPro, but PS has a limit on the number of installations. Seems that it's ~8, but I could well be wrong.
When that number has been reached, one needs to call Adobe Customer Service, and they can reset the installation numbers.
Like I stated, that is true for PS, but I'd expect PrPro to be similar. Even when the number of installations has been reached, a reset will get you back to zero.