Screen pop up is not displayed and caused parent screen freeze

Environment:

Oracle Forms 11g R2.

Java version 7

Oracle DB: 11g R2

OS Windows 7 client OS

When this happens: Only when we are using webutil (nailed down to webutilbsae.htm, webutiljpi.htm two files)

Problem: We have a form which you could make a query, popup screen should show up whenever we try to make a query. This popup screen asks the user if it is "default query". However, this popup never shows up and it seems to me it is hidden in the background which causes our "parent" screen grayed out - freezes. We have to kill the browser eventually. This only happens when we are using webutilbase.htm and webutiljpi.htm two original files.