I have been getting error listed below when trying to add a user to the system or change user right access

OpenERP Server Error Client Traceback (most recent call last): File "/usr/lib/pymodules/python2.7/openerp/addons/web/http.py", line 204, in dispatch response["result"] = method(self, *self.params) File "/usr/lib/pymodules/python2.7/openerp/addons/web/controllers/main.py", line 1128, in call_kw return self._call_kw(req, model, method, args, kwargs) File "/usr/lib/pymodules/python2.7/openerp/addons/web/controllers/main.py", line 1120, in _call_kw return getattr(req.session.model(model), method)(args, **kwargs) File "/usr/lib/pymodules/python2.7/openerp/addons/web/session.py", line 42, in proxy result = self.proxy.execute_kw(self.session._db, self.session._uid, self.session._password, self.model, method, args, kw) File "/usr/lib/pymodules/python2.7/openerp/addons/web/session.py", line 30, in proxy_method result = self.session.send(self.service_name, method, *args) File "/usr/lib/pymodules/python2.7/openerp/addons/web/session.py", line 103, in send raise xmlrpclib.Fault(openerp.tools.ustr(e), formatted_info)

Server Traceback (most recent call last): File "/usr/lib/pymodules/python2.7/openerp/addons/web/session.py", line 89, in send return openerp.netsvc.dispatch_rpc(service_name, method, args) File "/usr/lib/pymodules/python2.7/openerp/netsvc.py", line 292, in dispatch_rpc result = ExportService.getService(service_name).dispatch(method, params) File "/usr/lib/pymodules/python2.7/openerp/service/web_services.py", line 626, in dispatch res = fn(db, uid, params) File "/usr/lib/pymodules/python2.7/openerp/osv/osv.py", line 188, in execute_kw return self.execute(db, uid, obj, method, *args, *kw or {}) File "/usr/lib/pymodules/python2.7/openerp/osv/osv.py", line 131, in wrapper return f(self, dbname, args, *kwargs) File "/usr/lib/pymodules/python2.7/openerp/osv/osv.py", line 197, in execute res = self.execute_cr(cr, uid, obj, method, args, *kw) File "/usr/lib/pymodules/python2.7/openerp/addons/audittrail/audittrail.py", line 513, in execute_cr return self.log_fct(cr, uid, model, method, fct_src, args, *kw) File "/usr/lib/pymodules/python2.7/openerp/addons/audittrail/audittrail.py", line 294, in log_fct old_values = self.get_data(cr, uid_orig, pool, res_ids, model, method) File "/usr/lib/pymodules/python2.7/openerp/addons/audittrail/audittrail.py", line 338, in get_data values_text[field] = self.get_value_text(cr, SUPERUSER_ID, pool, resource_pool, method, field, resource[field]) File "/usr/lib/pymodules/python2.7/openerp/addons/audittrail/audittrail.py", line 193, in get_value_text field_obj = (resource_pool._all_columns.get(field)).column AttributeError: 'NoneType' object has no attribute 'column'