Make_invoice wizard from SO needs correction

This unsolved error is becoming a real problem. We've tested in demo and it works fine so we know how it is supposed to work.

To recap :
1. create Sales Order
2. select by checkbox to "Make Invoices" (leave "group invoices" unchecked)
3. creates Draft Invoices out of whichever Sales Orders we selected [#3 is what fails in live system and creates an Application Error]

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Traceback (most recent call last):
  File "/mnt/openerp/server/bin/netsvc.py", line 244, in dispatch
    result = LocalService(service_name)(method, *params)
  File "/mnt/openerp/server/bin/netsvc.py", line 73, in __call__
    return getattr(self, method)(*params)
  File "/mnt/openerp/server/bin/service/web_services.py", line 635, in execute
    return self._execute(db, uid, wiz_id, datas, action, context)
  File "/mnt/openerp/server/bin/service/web_services.py", line 615, in _execute
    return wiz.execute(db, uid, self.wiz_datas[wiz_id], action, context)
  File "/mnt/openerp/server/bin/wizard/__init__.py", line 177, in execute
    res = self.execute_cr(cr, uid, data, state, context)
  File "/mnt/openerp/server/bin/wizard/__init__.py", line 82, in execute_cr
    res['action'] = result_def['action'](self, cr, uid, data, context)
  File "/mnt/openerp/server/bin/addons/sale/wizard/make_invoice.py", line 49, in _makeInvoices
    order_obj.action_invoice_create(cr, uid, data['ids'], data['form']['grouped'])
  File "/mnt/openerp/server/bin/addons/sale/sale.py", line 403, in action_invoice_create
    created_lines = self.pool.get('sale.order.line').invoice_line_create(cr, uid, lines)
  File "/mnt/openerp/server/bin/addons/account_analytic_plans/account_analytic_plans.py", line 383, in invoice_line_create
    create_ids = super(sale_order_line,self).invoice_line_create(cr, uid, ids, context)
  File "/mnt/openerp/server/bin/addons/account_analytic_default/account_analytic_default.py", line 107, in invoice_line_create
    sale_line_obj = self.browse(cr, uid, ids[0], context)
IndexError: list index out of range