TOOLKIT_MODAL dialog is behaving like a Modeless dialog on SolSparc10-JDS with Mozilla 1.7

I have loaded an applet on Mozilla 1.7 in SolSparc10-JDS with Mustang-b73 plugin. Applet contains a button. On clicking the button, a TOOLKIT-MODAL dialog is shown. This modal dialog does not have any parent and being toolkit modal, it is supposed to block all the windows including the browser. But currently, it behaves like a modeless dialog where it does not block anything.

This is reproducible only on XToolkit with Mozilla 1.7. Not reproducible in NS7 on WinXP. This works fine on the same platform with Appletviewer.

I have attached a sample test with a HTML file. Open the HTML file in the specified browser. Click on the 'Load Image' button. A dialog will open up with a title 'Null Parent Toolkit Modal'. Once the dialog is shown, try clicking the same button again and the menus on the browser. If nothing is blocked, the bug is reproduced.