I jointly filed I-751 with my wife at VSC in December of 2001. The NOC i received was back in 12/2001 but today I received another NOC from VSC dated 08/18/2003 stating it could take up to 330 days to process this case, Travel and work is authorized. COuld please tell me why am I receiving another NOC instead of an approval notice since its been almost 18 months since I filed my 1-751. Your comments and suggestions would be really appreciated. Thanks

You file might be under Administrative processing for some reason which is taking that long. Just wait and see. You can do nothing in the matter till you receive their final decision.
Good luck.