Uninstall your Kindle 4 PC and start again. Go to Norton 360 and make sure it is DISABLED before you start the install.
Then download and install Kindle 4 PC Version 1.4.1 (31629). Then go to Norton 360, re-enable it and go to program management in Norton 360. From there enable Kindle 4 PC to have full outgoing and incoming priveleges.
Then Kindle 4 PC should work fine.