Failed to create monitors

I am trying to configure Applications Manager to monitor two oracle databases and two jboss servers. We are running Oracle 10.2.0.1 and JBoss 3.2.7. When I try to create the monitor (oracle or jboss), it fails but the message is simply "null". The oracle listener is running and I have verified that the user/password works by connecting using sqlplus. If I try to create the monitor with the wrong password or database sid, etc, I get an error message stating what is wrong, but when I have all of the information correct, the string "null" appears in the message area and it still fails. The story is similar for jboss. I have verified that jboss is running and that I am connecting to the correct port (by connecting from my browser) but I creating the monitor still fails. Has anyone seen anything like this before?

-Dennis