The RHQ 1.3 and Jopr 2.3.1 installer has a little issue (see RHQ-2222 jira), where it clears out the database password when you click on "Test connection".
Lets have a look at a screen shot:
When setting a database password (green circle) and then testing the connection (orange circle), the password will be reset and the install will fail later on.
If you are using the embedded H2 database, just re-select it in the drop down (violet circle) to have the database password filled in again by the system. Actually with H2, there is no need to test the connection in the first place :-)