You are missing the key line. You _must_ read the port.
You _cannot_ clear this interrupt, till the port is read. It'll retrigger automatically if this is not done.
You don't need to clear the inter ...
This is dependant on what happens to the pins on power on.
The 'changed' interrupt, is called, whenever the state of the pins 'disagrees, with the value stored in an internal latch on the chip. This ...