There are couple of things you can investigate. I noticed that the samples have a sleep after the user creation which is called before the password change. I am not aware of any documented requirement for the sleep but it does appear to help
Thread.currentThread().sleep(300);
Also, did you add the line MODE=ASF to your webi.properties file which is found in wijsp\WEB-INF\classes? The SDK documentation indicates it is required.
The configuration requirement is documented in the Developer Suite help file adminsdkEN.chm (Developer Suite 6.1). It can be found in the “Before you start” section of Customizing Adminstration. I am not aware of other configurations that are documented for use with the Admin SDK. However, I have not experimented with alternative configurations.
Did you ever find a fix for this? I am having the same problem in a program that was working a couple of months ago. I haven’t changed anything in the program (haven’t even recompiled it since it was last working).
So I’m guessing it must be a server/configuration problem.