OpenERP many2one field return, normally, the field name of the relation class. For Example, if I have a many2one to res_partner, I will read the partner name in the relative field. A solution is to set the rec name of the class on the field that you want read. For example, if I want to read the partner's phone number (it's a stupid example, sorry!) I must do this in my module:

class mail_alias(osv.Model):
    _inherit = 'res.partner'
    _rec_name = 'phone'

So, I obtain the phone in many2one.

Another solution is to use a relation field that read the correct value passing by youa many2one

phone = 'model': fields.related('your_many2one', 'phone', type='char', string='Phone                  size=128, select=True, store=False, readonly=True),