Index: openacs-4/packages/eduwiki/tcl/eduwiki-xowiki-procs.tcl
===================================================================
RCS file: /usr/local/cvsroot/openacs-4/packages/eduwiki/tcl/eduwiki-xowiki-procs.tcl,v
diff -u -r1.1 -r1.2
--- openacs-4/packages/eduwiki/tcl/eduwiki-xowiki-procs.tcl	7 Oct 2009 19:11:52 -0000	1.1
+++ openacs-4/packages/eduwiki/tcl/eduwiki-xowiki-procs.tcl	9 Nov 2009 19:06:04 -0000	1.2
@@ -24,10 +24,17 @@
     }
 
     Package instproc destroy {} {
-	::xowiki::Link instmixin delete ::eduwiki::EduWikiLink
-	::xowiki::Page instmixin delete ::eduwiki::EduWikiPage
-	::xowiki::WikiForm instmixin delete ::eduwiki::EduWikiForm
-        next
+	#
+	# In general, it is possible, that multiple eduwiki packages are
+	# concurrently active in one thread.  We want to remove the mixin only,
+	# when the last instance is deleted.
+	#
+	if {[llength [[self class] allinstances]] == 1} {
+	    ::xowiki::Link instmixin delete ::eduwiki::EduWikiLink
+	    ::xowiki::Page instmixin delete ::eduwiki::EduWikiPage
+	    ::xowiki::WikiForm instmixin delete ::eduwiki::EduWikiForm
+	}      
+	next
     }
 
     Package instproc return_page {