to reproduce:
1.) run bitcoin, wait for it to connect to net
2.) recycle your dynamic IP (get a new one)
3.) wait for next block
4.) see that new blocks don't show up in your client

expected behaviour:
bitcoin should detect that it's disconnected from the network and reconnect.

notes:
1.) the client still shows connection count after the IP change
2.) the connection count will slowly drop to 0
3.) then it will just sit there with 0 connections