Alec, I suspect that the ticket id in the create() method is not converted to an int but has a PostgresSQL specific integer type causing the error. I can't test it since I don't have a working PostgreSQL environment.
Kai, could you try to apply the following patch which adds an explicit type conversion before returning the ticket id to your Trac XML-RPC plug-in:
Index: tracrpc/ticket.py
===================================================================
--- tracrpc/ticket.py (revision 2617)
+++ tracrpc/ticket.py (working copy)
@@ -90,7 +90,7 @@
self.log.exception("Failure sending notification on creation "
"of ticket #%s: %s" % (t.id, e))
- return t.id
+ return int(t.id)
def update(self, req, id, comment, attributes = {}, notify=False):
""" Update a ticket, returning the new ticket in the same form as getTicket(). """
