Many use NVU to edit their web pages with great success. The “Incorrect Login” error message you received is likely indicating that you have incorrect values in the Publish Settings’ screen (assuming that your site is fuilly “live” - DNS has propagated and it is reachable from the web using your domain name in the url.)
Have you tried logging into your site’s space via ftp or logging into the shell on your server using ssh (or telnet)?
You should start your troubleshooting there, as once you can login via ftp, then you will have confirmed what settings are necessary for inclusion in the NVU “Publish Settings” screen. Additionally, you can always move the pages you edit with NVU to and from your site via FTP instead of the ‘Pulbish’ feature of NVU (which is what I often do- I just like it better that way [ink]).