Create Login Problem In SQL Server 2005

Hey guys,

I'm having a problem making a new login inside the sql management studio, the problem is, when i create a new login, i selected SQL Authentication, then type a password, then uncheck Enforce password policy.

i then select the database i want the login to be associated with, but once i click ok i get this exception:
Create failed for Login ''. (Microsoft.SqlServer.Smo)

An exception occurred while executing a Transact-SQL statement or batch. (Microsoft.SqlServer.ConnectionInfo)
"An object or column name is missing or empty. For SELECT INTO statements, verify each column has a name. For other statements, look for empty alias names. Aliases defined as "" or [] are not allowed. Add a name or single space as the alias name. (Microsoft SQL Server, Error: 1038)

I even tried with Northwind and a brand new database with a table and 2 columns but it's the same story every time.
Any ideas?

Thanks a bunch