OS Tested: Windows XP Home SP2, Windows 2000 Professional
Steps to reproduce:

1. Install previous version of Java other than 5u6 ie: 5u3b7 [one I used]
2. In regedit: Create new String Value namely UpdateServletURL here:
HKEY_LOCAL_MACHINE\SOFTWARE\JavaSoft\Java Update\Policy
Give this the value: http://latte.ireland.sun.com/update/1.5.0/map-1.5.0_06.xml
3. Go to Java Control Panel for 5u3
4. Click on Update tab and button 'Update Now'
5. Observe the following -

Java Update Bubble appears in system tray - Ready to download - Click this
Java Update Bubble appears in system tray - Ready to install - Click this

After a few seconds you will see - preparing to install in the windows-installer shield
then you get an error message -

"Internal Error 2229: See the attached screen shot for full error message.

NOTE: I have not staged Java Update for 5u6_plus_b4 on latte.ireland.sun.com
I have simply created a map file containing some versions that I am testing the update from and which points to another xml file called http://latte.ireland/update/1.5.0/1.5.0_06-test.xml - This points to actual staged java update on http://java.sun.com/webapps/download/AutoDL%3FBundleId=10342