Index: openacs-4/packages/acs-authentication/tcl/authentication-procs.tcl
===================================================================
RCS file: /usr/local/cvsroot/openacs-4/packages/acs-authentication/tcl/authentication-procs.tcl,v
diff -u -r1.75 -r1.76
--- openacs-4/packages/acs-authentication/tcl/authentication-procs.tcl	10 Jan 2007 21:22:01 -0000	1.75
+++ openacs-4/packages/acs-authentication/tcl/authentication-procs.tcl	18 Jan 2007 11:57:19 -0000	1.76
@@ -47,8 +47,32 @@
         set message [_ acs-subsite.lt_Your_login_has_expire]
     }
 
+    set return_url [ad_get_login_url -return]
+
+    # Long URLs (slightly above 4000 bytes) can kill aolserver-4.0.10, causing
+    # a restart. They lead to empty Bowser-windows with aolserver 4.5 (but no 
+    # crash so far). May browsers have length limitations for URLs. E.g. 
+    # 2083 is the documented maximal length of MSIE.
+    #
+    # Long URLs will be generated e.g. when 
+    #   a) a user edits a form with text entries
+    #   b) before submitting the form logs out of OpenACS from a different browser window
+    #   c) submits the form. 
+    #
+    # When submitting needs authentication, OpenACS generates the redirect to 
+    # /register with the form-data coded into the URL to continue there.....
+    #
+    # set user_agent [string tolower [ns_set get [ns_conn headers] User-Agent]]
+    # ns_log notice "URL have url, len=[string length $return_url] $user_agent"
+
+    set url_too_long [expr {[string length $return_url] > 2083}]
+    if {$url_too_long} {
+      set message "URL too long. If you were editing a from, please use the back button after logginin and resubmit the form" 
+      set return_url "."
+    }
+
     # The -return switch causes the URL to return to the current page
-    ad_returnredirect -message $message -- [ad_get_login_url -return]
+    ad_returnredirect -message $message -- $return_url
     ad_script_abort
 }