Index: openacs-4/packages/acs-tcl/tcl/security-procs.tcl
===================================================================
RCS file: /usr/local/cvsroot/openacs-4/packages/acs-tcl/tcl/security-procs.tcl,v
diff -u -r1.70 -r1.71
--- openacs-4/packages/acs-tcl/tcl/security-procs.tcl	18 Apr 2011 20:57:43 -0000	1.70
+++ openacs-4/packages/acs-tcl/tcl/security-procs.tcl	18 Apr 2011 21:25:34 -0000	1.71
@@ -97,10 +97,15 @@
     } else {
 	# The session cookie already exists and is valid.
 	set cookie_data [split [lindex $cookie_list 0] {,}]
-	set session_expr [expr {[lindex $cookie_data 3] + [sec_session_timeout]}]
-    if {![string is integer -strict $session_expr] || $session_expr < [ns_time]} {
+	set session_last_renew_time [lindex $cookie_data 3]
+    if {[string is integer -strict $session_last_renew_time]} {
+        set session_expr \
+            [expr {$session_last_renew_time + [sec_session_timeout]}]
+    }
+    if {![info exists session_expr] || $session_expr < [ns_time]} {
         sec_login_handler
     }
+               
 	set session_id [lindex $cookie_data 0]
 	set untrusted_user_id [lindex $cookie_data 1]
 	set login_level [lindex $cookie_data 2]