Exception Dialog boxes are not shown all times in the same browser session

When an Exception dialog box is pop up and the user responds with the
"OK" and goes back in the browser and visits another page which also
also throws the Exception and the Exception Dialog box which is
expected doesnot popup all the time on Solaris 8/ Netscape 6 and Nestcape 4.x.
The same behaviour is seen on windows but not everytime.
On solaris, It sometimes hangs the browser.

To reproduce the problem :

1. Install Java Plug-in Merlin Build 50
2. Run the Test cases I)Unified Error and warning dialog.

  1 , 2 and 3 under Test cases for Exception Dialog Boxes.

3. Visit Test case 1 click "OK" to the Exception Dialog box.

4.In the same browser session click back and run test case 2

The Exception dialog box doesnot popup this time.

URL for the test cases :

http://sqesvr.eng.sun.com/deployment1/ws/doc/proc/JPI_AUE.html