diff -r bfa6bee1a9e0 trytond/protocols/jsonrpc.py
--- a/trytond/trytond/protocols/jsonrpc.py	Mon Oct 20 14:30:02 2014 +0200
+++ b/trytond/trytond/protocols/jsonrpc.py	Mon Nov 03 13:32:30 2014 +0100
@@ -27,6 +27,7 @@
     import json
 import base64
 import encodings
+import logging
 try:
     from cStringIO import StringIO
 except ImportError:
@@ -136,7 +137,14 @@
         existing method through subclassing is the prefered means
         of changing method dispatch behavior.
         """
-        rawreq = json.loads(data, object_hook=JSONDecoder())
+        try:
+            rawreq = json.loads(data, object_hook=JSONDecoder())
+        except:
+            exc_type, exc_value = sys.exc_info()[:2]
+            logging.getLogger('jsonrpc').warning(
+                'Exception in JSONRPC dispatcher: %s (%s)\n  %s'
+                % (exc_value, exc_type, traceback.format_exc()))
+            raise

         req_id = rawreq.get('id', 0)
         method = rawreq['method']
@@ -152,11 +160,18 @@
                 response['result'] = self._dispatch(method, params)
         except (UserError, UserWarning, NotLogged,
                 ConcurrencyException), exception:
+            logging.getLogger('jsonrpc').warning('User Error: %s (%s)'
+                % (method, params))
+            traceback.print_exc()
             response['error'] = exception.args
         except Exception:
+            exc_type, exc_value = sys.exc_info()[:2]
             tb_s = ''.join(traceback.format_exception(*sys.exc_info()))
             for path in sys.path:
                 tb_s = tb_s.replace(path, '')
+            logging.getLogger('jsonrpc').warning(
+                'Exception in JSONRPC response generation: %s (%s)\n  %s'
+                % (exc_value, exc_type, tb_s))
             # report exception back to server
             response['error'] = (str(sys.exc_value), tb_s)