not properly dreg & drop tasks in kanban view

[Mayur Maheshwari(OpenERP)]

on latest revision (addons, server, web)

step to reproduce ---<>|

==> open a kanban view of tasks
==> dreg the any task to testing stage to deployment stage and again put it to back deployment to testing stage

got a trace back

Server Traceback (most recent call last):
  File "/home/odoo/runbot/static/openerp-dev-trunk-11178/server/openerp/addons/web/common/http.py", line 607, in send
    result = openerp.netsvc.dispatch_rpc(service_name, method, args)
  File "/home/odoo/runbot/static/openerp-dev-trunk-11178/server/openerp/netsvc.py", line 362, in dispatch_rpc
    result = ExportService.getService(service_name).dispatch(method, params)
  File "/home/odoo/runbot/static/openerp-dev-trunk-11178/server/openerp/service/web_services.py", line 586, in dispatch
    res = fn(db, uid, *params)
  File "/home/odoo/runbot/static/openerp-dev-trunk-11178/server/openerp/osv/osv.py", line 167, in execute_kw
    return self.execute(db, uid, obj, method, *args, **kw or {})
  File "/home/odoo/runbot/static/openerp-dev-trunk-11178/server/openerp/osv/osv.py", line 121, in wrapper
    return f(self, dbname, *args, **kwargs)
  File "/home/odoo/runbot/static/openerp-dev-trunk-11178/server/openerp/osv/osv.py", line 176, in execute
    res = self.execute_cr(cr, uid, obj, method, *args, **kw)
  File "/home/odoo/runbot/static/openerp-dev-trunk-11178/server/openerp/addons/audittrail/audittrail.py", line 494, in execute_cr
    return fct_src(cr, uid, model, method, *args, **kw)
  File "/home/odoo/runbot/static/openerp-dev-trunk-11178/server/openerp/osv/osv.py", line 164, in execute_cr
    return getattr(object, method)(cr, uid, *args, **kw)
  File "/home/odoo/runbot/static/openerp-dev-trunk-11178/server/openerp/addons/project_timesheet/project_timesheet.py", line 274, in write
    return super(task,self).write(cr, uid, ids, vals, context)
  File "/home/odoo/runbot/static/openerp-dev-trunk-11178/server/openerp/addons/project/project.py", line 1098, in write
    result = super(task,self).write(cr, uid, ids, vals, context=context)
  File "/home/odoo/runbot/static/openerp-dev-trunk-11178/server/openerp/addons/base/ir/ir_needaction.py", line 163, in write
    write_res = super(ir_needaction_mixin, self).write(cr, uid, ids, values, context=context)
  File "/home/odoo/runbot/static/openerp-dev-trunk-11178/server/openerp/addons/mail/mail_thread.py", line 91, in write
    write_res = super(mail_thread, self).write(cr, uid, ids, vals, context=context);
  File "/home/odoo/runbot/static/openerp-dev-trunk-11178/server/openerp/osv/orm.py", line 3950, in write
    'where id IN %s', upd1 + [sub_ids])
  File "/home/odoo/runbot/static/openerp-dev-trunk-11178/server/openerp/sql_db.py", line 152, in wrapper
    return f(self, *args, **kwargs)
  File "/home/odoo/runbot/static/openerp-dev-trunk-11178/server/openerp/sql_db.py", line 212, in execute
    res = self._obj.execute(query, params)
TransactionRollbackError: could not serialize access due to concurrent update

Thanks.
Mayur