i purchased mine from MobilePhonesDirect. I checked with them to see if the warranty covers the Micro USB Port. They responded by saying:
The warranty will not cover physical damage, if it is an inherent fault and Nokia would need to admit it is a manufacturing defect then it would be covered under the warranty, Nokia have not made such claims to my knowledge so it would be a case of physical damage, for clarification please call Nokia Care on 08450455555