Error when allocating Holidays

[Harmel Delphine (OpenERP)]

* Create a Leave type "Casual Leave" and check "Apply Double Validation"
* Create an Allocation Request with the type "Casual Leave"

=> It's not possible to define the "First Approval" and "Second Approval" fields

* Save it

=> you get the following error :

Environment Information :
System : Linux-2.6.32-26-generic-i686-with-Ubuntu-10.04-lucid
OS Name : posix
Distributor ID: Ubuntu
Description: Ubuntu 10.04.1 LTS
Release: 10.04
Codename: lucid
Operating System Release : 2.6.32-26-generic
Operating System Version : #48-Ubuntu SMP Wed Nov 24 09:00:03 UTC 2010
Operating System Architecture : 32bit
Operating System Locale : fr_BE.UTF8
Python Version : 2.6.5
OpenERP-Client Version : 6.0.0-rc1-1
Last revision No. & ID :1713 launchpad_translations_on_behalf_of_openerp-20101211044634-hs30hc0l5ufmah4a
Traceback (most recent call last):
  File "/home/openerp/trunk/server/bin/netsvc.py", line 489, in dispatch
    result = ExportService.getService(service_name).dispatch(method, auth, params)
  File "/home/openerp/trunk/server/bin/service/web_services.py", line 598, in dispatch
    res = fn(db, uid, *params)
  File "/home/openerp/trunk/server/bin/osv/osv.py", line 119, in wrapper
    return f(self, dbname, *args, **kwargs)
  File "/home/openerp/trunk/server/bin/osv/osv.py", line 203, in execute
    res = pool.execute_cr(cr, uid, obj, method, *args, **kw)
  File "/home/openerp/trunk/server/bin/osv/osv.py", line 193, in execute_cr
    return getattr(object, method)(cr, uid, *args, **kw)
  File "/home/openerp/trunk/server/bin/addons/hr_holidays/hr_holidays.py", line 205, in create
    return super(hr_holidays, self).create(cr, uid, vals, context=context)
  File "/home/openerp/trunk/server/bin/osv/orm.py", line 3768, in create
    self._validate(cr, user, [id_new], context)
  File "/home/openerp/trunk/server/bin/osv/orm.py", line 1055, in _validate
    if not fun(self, cr, uid, ids):
  File "/home/openerp/trunk/server/bin/addons/hr_holidays/hr_holidays.py", line 254, in _check_date
    date_from = time.strptime(rec['date_from'], '%Y-%m-%d %H:%M:%S')
  File "/usr/lib/python2.6/_strptime.py", line 454, in _strptime_time
    return _strptime(data_string, format)[0]
  File "/usr/lib/python2.6/_strptime.py", line 322, in _strptime
    found = format_regex.match(data_string)
TypeError: expected string or buffer