Error When Generating a Manufacturing Order

Hello,
I have installed Open Erp version 6.0.3 on Debian and I was happy with it since last two months with no issues at all. Lately I am facing some issue with Manufacturing. When I try to create a Manufacturing order it gives me the error below

Traceback (most recent call last):
File "/opt/openerp/server/bin/netsvc.py", line 489, in dispatch
result = ExportService.getService(service_name).dispatch(method, auth, params)
File "/opt/openerp/server/bin/service/web_services.py", line 599, in dispatch
res = fn(db, uid, *params)
File "/opt/openerp/server/bin/osv/osv.py", line 122, in wrapper
return f(self, dbname, *args, **kwargs)
File "/opt/openerp/server/bin/osv/osv.py", line 176, in execute
res = self.execute_cr(cr, uid, obj, method, *args, **kw)
File "/opt/openerp/server/bin/osv/osv.py", line 167, in execute_cr
return getattr(object, method)(cr, uid, *args, **kw)
File "/opt/openerp/server/bin/osv/orm.py", line 3696, in create
self.pool.get(object)._store_set_values(cr, user, ids, fields2, context)
File "/opt/openerp/server/bin/osv/orm.py", line 3790, in _store_set_values
result = self._columns[val[0]].get(cr, self, ids, val, 1, context=context)
File "/opt/openerp/server/bin/osv/fields.py", line 802, in get
res = self._fnct(cr, obj._table, ids, name, self._arg, context)
File "/opt/openerp/server/bin/addons/mrp.zip/mrp/mrp.py", line 412, in _production_calc
for prod in self.browse(cr, uid, ids, context=context):
File "/opt/openerp/server/bin/sql_db.py", line 78, in wrapper
return f(self, *args, **kwargs)
File "/opt/openerp/server/bin/sql_db.py", line 237, in __getattr__
return getattr(self._obj, name)
AttributeError: 'cursor' object has no attribute 'browse'

Nothing has changed actually my set up is the same. Lately since last two weeks, I am not able to create Manufacturing Order. I was able to create it earlier. Because of this issue I created another database and I did all the required settings like creating products, creating customers. I can create Sales Order, Purchase Order I can validate the Invoice from Accounting but when I try to create Manufacture Order it gives me the above error.

Thanks in advance
Kaushik