Comment 2 for bug 1257865

I came across this also. That's because of the order in which the view fiel where declared in hr_schedule/__opernerp__.py. it appears that an id was requested before it was even declared. rearranging worked for me.
this workede for me

'data': [
        'wizard/schedule_ot_by_employees.xml',
        'hr_schedule_view.xml',
        'security/groups.xml',
        'security/ir.model.access.csv',
        'security/ir_rule.xml',
        'data/hr_schedule_data.xml',
        'wizard/validate_schedule_view.xml',
        'wizard/compute_alerts_view.xml',
        'wizard/generate_schedules_view.xml',
        'wizard/restday_view.xml',
        'hr_schedule_data.xml',
        'hr_schedule_workflow.xml',
        'hr_schedule_cron.xml',
        'schedule_ot_batch_workflow.xml',
        'schedule_ot_workflow.xml',
        'alert_rule_data.xml',
    ],