Relevant log entries in apache log:
[Mon Jan 13 09:45:43 2014] [error] [client 000.000.000.000] Traceback (most recent call last):
[Mon Jan 13 09:45:43 2014] [error] [client 000.000.000.000] File "/usr/lib/pymodules/python2.7/web/application.py", line 242, in process
[Mon Jan 13 09:45:43 2014] [error] [client 000.000.000.000] return self.handle()
[Mon Jan 13 09:45:43 2014] [error] [client 000.000.000.000] File "/usr/lib/pymodules/python2.7/web/application.py", line 233, in handle
[Mon Jan 13 09:45:43 2014] [error] [client 000.000.000.000] return self._delegate(fn, self.fvars, args)
[Mon Jan 13 09:45:43 2014] [error] [client 000.000.000.000] File "/usr/lib/pymodules/python2.7/web/application.py", line 415, in _delegate
[Mon Jan 13 09:45:43 2014] [error] [client 000.000.000.000] return handle_class(cls)
[Mon Jan 13 09:45:43 2014] [error] [client 000.000.000.000] File "/usr/lib/pymodules/python2.7/web/application.py", line 390, in handle_class
[Mon Jan 13 09:45:43 2014] [error] [client 000.000.000.000] return tocall(*args)
[Mon Jan 13 09:45:43 2014] [error] [client 000.000.000.000] File "/usr/share/apache2/iredadmin/controllers/decorators.py", line 11, in proxyfunc
[Mon Jan 13 09:45:43 2014] [error] [client 000.000.000.000] return func(self, *args, **kw)
[Mon Jan 13 09:45:43 2014] [error] [client 000.000.000.000] File "/usr/share/apache2/iredadmin/controllers/amavisd/log.py", line 154, in GET
[Mon Jan 13 09:45:43 2014] [error] [client 000.000.000.000] page = int(quarantined_type) or 1
[Mon Jan 13 09:45:43 2014] [error] [client 000.000.000.000] TypeError: int() argument must be a string or a number, not 'NoneType'
[Mon Jan 13 09:45:43 2014] [error] [client 000.000.000.000]