Java Control Panel does not find the Firefox browser

SNV b36, vermillion(JDS4), sparc and x86. Jdk1.5.0_06-04. Firefox is the only browser on the system.

steps:

1. Start Java Control Panel
2. Click the Advanced tab
3. Click the Command to launch default browser

expected result:
the path of the firefox borwser should be shown

actual result:
<No Browser Selected>

Install mustang manually, get the same result.