Here are the workarounds: 
Workaround 1 
=============== 

1. Exit the Builder and OC4J 
2. Open cauprefs.ora (located in the Oracle Home root directory) 
3. Locate the lines labeled "Forms.html ..." 
4. Make your changes here. Any values you do not want displayed in the 
Builder replace with (). Example below. 
5. Save the file and restart the Builder 

Example of a correct cauprefs.ora entry 
----------------------------------------- 
Forms.html = "http://myMachine:8888/forms90/f90servlet" 
Forms.html1 = () 
Forms.html2 = () 
Forms.html3 = () 
Forms.html4 = () 
Forms.html5 = () 

The machine.domain name should NOT contain spaces. This is poor naming 
practice regardless of the use of Forms. 

Workaround 2 
============== 

Go to the preferences dialog box and click on the Runtime tab. 
Set Web Browser (i.e, C:Program FilesInternet ExplorerIEXPLORE.EXE) . 

Workaround 3 
============= 

Go to the preferences dialog box and click on the Runtime tab. Make 
sure your Application Server field is correct. 

Workaround 4 
=============== 

1. Go to the preferences dialog box and click on the Runtime tab and then 
make Application Server field Blank. 

Workaround 5 
============== 

%20 is the escape for blank. Maybe you have a blank character in the 
runtime settings.