SharePoint 2010 database attach 404 error

Hello Everybody, I moved a content database from one environment to another environment with database attach. When I browse the site I get a 404 no found error. The environment where i took the database from has a custom master page for website layout and the standard v4.master for the site settings. So in the new environment i try to browse directly the website settings page with http://serverurl/_layouts/settings.aspx and it works i can browse the settings page. On the site settings page I set the v4.master as master page and did an inheritance to all subsites but still no luck when I browsed the page and every subsite I still get the 404 error. I took a look in the master page library http://serverurl/catalogs/master when I click on the v4.master or any other element in the library and go to show properties I get again the 404 error. I uploaded a new v4.master to the library and go to properties again 404. So far so good (or not really) after knocking my head to desk I create a new webapplication with new database and new site collection. And now the strange thing, I can browse the new site collection but when I go to master page catalog and click the v4.master and show properties I get again an 404 error with new database and new site collection. And this give me a bad feeling that I even get the error on a new site collection with new webapp and database. I reattached the database but still same error. No infos about the error in the USLogs Normally I would say ok seems that SharePoint had some trouble with the custom master page. But the 404 on the new site collection scared me a little bit. My next step is to set the master page on the productive environment to v4.master and take again a backup from the database and attach these one. Unfortunately I don’t access to the productive environment so I have to wait until Monday.   But maybe had someone a similar problem and knows a solution.