It happens at least here on t.e.o:
Traceback (most recent call last):
File "/usr/local/virtualenv/lib/python2.4/site-packages/Trac-0.11dev_r7225-py2.4.egg/trac/web/api.py", line 339, in send_error
'text/html')
File "/usr/local/virtualenv/lib/python2.4/site-packages/Trac-0.11dev_r7225-py2.4.egg/trac/web/chrome.py", line 708, in render_template
if not req.session or not int(req.session.get('accesskeys', 0)):
File "/usr/local/virtualenv/lib/python2.4/site-packages/Trac-0.11dev_r7225-py2.4.egg/trac/web/api.py", line 168, in __getattr__
value = self.callbacks[name](self)
File "/usr/local/virtualenv/lib/python2.4/site-packages/Trac-0.11dev_r7225-py2.4.egg/trac/web/main.py", line 257, in _get_session
return Session(self.env, req)
File "/usr/local/virtualenv/lib/python2.4/site-packages/Trac-0.11dev_r7225-py2.4.egg/trac/web/session.py", line 142, in __init__
self.get_session(req.authname, authenticated=True)
File "/usr/local/virtualenv/lib/python2.4/site-packages/Trac-0.11dev_r7225-py2.4.egg/trac/web/session.py", line 156, in get_session
super(Session, self).get_session(sid, authenticated)
File "/usr/local/virtualenv/lib/python2.4/site-packages/Trac-0.11dev_r7225-py2.4.egg/trac/web/session.py", line 56, in get_session
(sid, int(authenticated)))
File "/usr/local/virtualenv/lib/python2.4/site-packages/Trac-0.11dev_r7225-py2.4.egg/trac/db/util.py", line 50, in execute
return self.cursor.execute(sql_escape_percent(sql), args)
File "/usr/local/virtualenv/lib/python2.4/site-packages/Trac-0.11dev_r7225-py2.4.egg/trac/db/util.py", line 50, in execute
return self.cursor.execute(sql_escape_percent(sql), args)
ProgrammingError: current transaction is aborted, commands ignored until end of transaction block
Try editing any of the reports, insert an error and save it. You'll get the above "raw" backtrace (i.e. as text).
It must somehow be PostgreSQL specific, maybe the connection is not properly reset after the initial error and all subsequent use will fail (here while retrieving session info during rendering of the error page).