We recently migrated our Multi-domain magento setup from a shared host to a dedicated server.
All is working fine fronted, but when I try to go to the admin section
After migration from www.domain1.com/magento/ to www.domain2.com/magento/ I was getting 500 Internal Server Error. So I just renamed my .htaccess to htaccess.txt. And my frontend started working fine, But at Backend http://www.yourstore.com/admin/ I was getting Same 500 Internal Server error.
After trying many option suggested online nothing worked for me and after that I tried to access admin via following URL and voilà worked perfect, Hope this help others.
Try to access as this > http://www.yourstore.com/index.php/admin/