Java Security

I'm implementing authentication using JAAS (in Oracle 9iAS) in our application. We're using login modules that someone else has written. The problem is that I keep getting the exception:

javax.security.auth.login.LoginException: No LoginModules configured for AlwaysLogin
at javax.security.auth.login.LoginContext.init(LoginContext.java:176)
at javax.security.auth.login.LoginContext.<init>(LoginContext.java:319)

The java.security.auth.login.config system property is read in from the orion-application.xml file. The system property is being read in ok, but the app is unable to locate that actual file that the system property points to, e.g. c:\my.login.config. According to the javadocs:

The java.lang.System property java.security.auth.login.config may also be set to a URL pointing to another login configuration file

How do I need to refer to the file (e.g. c:/my.login.config or file:///c:/my.login.config etc.) to ensure that it will be read? I can't for the life of me figure out what is wrong.