Bug fixed:

  Certain ZEO server errors could cause a client to get into a state
  where it couldn't commit transactions.
  https://bugs.launchpad.net/zodb/+bug/374737

src/CHANGES.txt

@@ -41,6 +41,10 @@ Bugs Fixed
   Changed its sort parameter list to match that of its (Python 2.4+)
   UserList base class.
 
+- Certain ZEO server errors could cause a client to get into a state
+  where it couldn't commit transactions.
+  https://bugs.launchpad.net/zodb/+bug/374737
+
 3.9.0b5 (2009-08-06)
 ====================
 

src/ZEO/StorageServer.py

@@ -407,7 +407,7 @@ class ZEOStorage:
                 raise StorageTransactionError("Multiple simultaneous tpc_begin"
                                               " requests from one client.")
 
-        self.transaction = t = transaction.Transaction()
+        t = transaction.Transaction()
         t.id = id
         t.user = user
         t.description = description
@@ -421,6 +421,16 @@ class ZEOStorage:
         self.store_failed = 0
         self.stats.active_txns += 1
 
+        # Assign the transaction attribute last. This is so we don't
+        # think we've entered TPC until everything is set.  Why?
+        # Because if we have an error after this, the server will
+        # think it is in TPC and the client will think it isn't.  At
+        # that point, the client will keep trying to enter TPC and
+        # server won't let it.  Errors *after* the tpc_begin call will
+        # cause the client to abort the transaction.
+        # (Also see https://bugs.launchpad.net/zodb/+bug/374737.)
+        self.transaction = t
+
     def tpc_finish(self, id):
         if not self._check_tid(id):
             return