IP not resolving after A record change

I’ve pointed my DNS a record to the new IP of my multi-blog wordpress installation but when a person types the domain information into a browser it resolves to the new site, but shows the IP in the browser address bar instead of showing the domain name for each page.

When I went through and changed all the IP references in the database to the new domain name, now the pages give database errors (even when a new page is created, it gives a database error).

Is there something about this new multi-blog platform that requires a different approach to ensure that the domain resolves to all the pages and posts?