Error when string is in french language in xml

I have given string in french character for page in xml file. This was working fine with revno 2084 but now its not working and gives following error.
[2010-08-10 12:46:23,555] ERROR:web-services:[17]: Traceback (most recent call last):
[2010-08-10 12:46:23,556] ERROR:web-services:[18]: File "/home/eiffel/openerp/server/bin/osv/osv.py", line 58, in wrapper
[2010-08-10 12:46:23,556] ERROR:web-services:[19]: return f(self, dbname, *args, **kwargs)
[2010-08-10 12:46:23,556] ERROR:web-services:[20]: File "/home/eiffel/openerp/server/bin/osv/osv.py", line 119, in execute
[2010-08-10 12:46:23,556] ERROR:web-services:[21]: res = pool.execute_cr(cr, uid, obj, method, *args, **kw)
[2010-08-10 12:46:23,556] ERROR:web-services:[22]: File "/home/eiffel/openerp/server/bin/osv/osv.py", line 111, in execute_cr
[2010-08-10 12:46:23,556] ERROR:web-services:[23]: return getattr(object, method)(cr, uid, *args, **kw)
[2010-08-10 12:46:23,556] ERROR:web-services:[24]: File "/home/eiffel/openerp/server/bin/osv/orm.py", line 1371, in fields_view_get
[2010-08-10 12:46:23,556] ERROR:web-services:[25]: xarch, xfields = self.__view_look_dom_arch(cr, user, result['arch'], view_id, context=context)
[2010-08-10 12:46:23,557] ERROR:web-services:[26]: File "/home/eiffel/openerp/server/bin/osv/orm.py", line 1116, in __view_look_dom_arch
[2010-08-10 12:46:23,557] ERROR:web-services:[27]: fields_def = self.__view_look_dom(cr, user, node, view_id, context=context)
[2010-08-10 12:46:23,557] ERROR:web-services:[28]: File "/home/eiffel/openerp/server/bin/osv/orm.py", line 1111, in __view_look_dom
[2010-08-10 12:46:23,557] ERROR:web-services:[29]: fields.update(self.__view_look_dom(cr, user, f, view_id, context))
[2010-08-10 12:46:23,557] ERROR:web-services:[30]: File "/home/eiffel/openerp/server/bin/osv/orm.py", line 1111, in __view_look_dom
[2010-08-10 12:46:23,557] ERROR:web-services:[31]: fields.update(self.__view_look_dom(cr, user, f, view_id, context))
[2010-08-10 12:46:23,557] ERROR:web-services:[32]: File "/home/eiffel/openerp/server/bin/osv/orm.py", line 1111, in __view_look_dom
[2010-08-10 12:46:23,557] ERROR:web-services:[33]: fields.update(self.__view_look_dom(cr, user, f, view_id, context))
[2010-08-10 12:46:23,558] ERROR:web-services:[34]: File "/home/eiffel/openerp/server/bin/osv/orm.py", line 1111, in __view_look_dom
[2010-08-10 12:46:23,558] ERROR:web-services:[35]: fields.update(self.__view_look_dom(cr, user, f, view_id, context))
[2010-08-10 12:46:23,558] ERROR:web-services:[36]: File "/home/eiffel/openerp/server/bin/osv/orm.py", line 1103, in __view_look_dom
[2010-08-10 12:46:23,558] ERROR:web-services:[37]: node.set('string', trans)
[2010-08-10 12:46:23,558] ERROR:web-services:[38]: File "lxml.etree.pyx", line 634, in lxml.etree._Element.set (src/lxml/lxml.etree.c:31548)
[2010-08-10 12:46:23,558] ERROR:web-services:[39]: File "apihelpers.pxi", line 487, in lxml.etree._setAttributeValue (src/lxml/lxml.etree.c:13896)
[2010-08-10 12:46:23,559] ERROR:web-services:[40]: File "apihelpers.pxi", line 1242, in lxml.etree._utf8 (src/lxml/lxml.etree.c:19848)
[2010-08-10 12:46:23,559] ERROR:web-services:[41]: ValueError: All strings must be XML compatible: Unicode or ASCII, no NULL bytes

It also gives error for string of field in french character.