Hi I have a problem with my openerp while trying to activate developper mode I got this error

{"message": "OpenERP WebClient Error", "code": 300, "data": {"debug": "Client Traceback (most recent call last):\n File \"C:\\OpenERP\\Server\\server\\openerp\\addons\\web\\http.py\", line 285, in dispatch\n File \"C:\\OpenERP\\Server\\server\\openerp\\addons\\web\\controllers\\main.py\", line 581, in index\nUnicodeDecodeError: 'ascii' codec can't decode byte 0xc3 in position 235: ordinal not in range(128)\n", "type": "client_exception"}}

Please help me to solve this