<blockquote>Appearantly the ISP is only supplying 1 day leases.
The lease changed early this morning before I booted the laptop. There is a different IP address than yesterday. But I didn't receive the "New Wireless" pop-up this morning.</blockquote>
The changes of the assigned IP by the internet provider does not concern the IP that is assigned to the computer by the router or nat-enabled modem.
Any IP assigned to the computer by the router or modem (with NAT) will be involved with a private network address, and not the public IP assigned by the provider.
How the network connection settings arranged? Is the ZA set to ask for every new wireless networks detected?
The ZA will detect a new network on startups if the router is assigning a new IP every time to the computer.This can be usually resolved by locking in the MAC of the computer in the router and setting the router to always assign the same IP to the computer every time.