I've noticed an interesting problem recently where my laptop will not automatically refresh my DHCP lease when changing between wireless networks. Instead, it will attempt to use the existing lease for the new network. Of course, since each network has different settings any connections will fail when using the old lease.
While Windows will eventually request a new DHCP lease, it's often much faster for me to release the old lease and request a new, correct, lease. It puzzles me as to why this is not automatically done when associating to the network? One possible cause is that the laptop is put to sleep while connected to one network, then woken when in range of the other network. Nevertheless, I would expect that the lease would be renewed when the laptop associates to the other network rather than attempting to use the old lease.
It should be noted that the two networks are completely different, both in terms of size, number of APs, network settings, SSIDs etc. One network is my home network and the other one is the campus-wide network at my University.