Forum OpenACS Q&A: Why auto logout when loaded java applet ???

When I loaded java applet embeded adp page as following code:
#########################################################
applet name="probemark" width="840" height="600" code="ProbeMark.class" archive="SignedProbeMark.jar"
#########################################################

Then I click to another page include [ad_get_user_id] or [ad_maybe_redirect_for_registration] , it would redirect to relogin page.
So it mean the session had been logout cause of java applet loaded ???
I check the cookies and DB session table between click before and after, but it had not changed anything.

What's wrong with the situation ???