diff -r 0bce018bc7d7 -r 0b5639aa2dac server/session.py
--- a/server/session.py	Thu Nov 17 18:19:56 2011 +0100
+++ b/server/session.py	Mon Nov 21 17:53:14 2011 +0100
@@ -994,6 +994,7 @@
                     # instead of having to implements rollback, revertprecommit
                     # and revertcommit, that will be enough in mont case.
                     operation.failed = True
+                    self.critical('operation precommit failed for %s', operation.__class__.__name, exc_info=True)
                     for operation in reversed(processed):
                         try:
                             operation.handle_event('revertprecommit_event')