Ok. This is really weird. This has happened on two different machines now.
Problem: You have just installed NetBeans 7.1 Java EE version on Windows 7 64 bit and you want to look at the Administration Console. You open a URL to localhost:4848. You are prompted for a user name and password. Nothing works.
For years the default login for GlassFish on NetBeans has been:
Solution 3/10/12: This is a bug with Glashfish 3.1.1 and Java 7. Update to Glassfish 3.1.2 (included in NetBeans 7.1.1) and the admin console should work. Or if you need to use 3.1.1 for some reason, you can fall back to JDK 6. Either approach should work.