oof owa exch 2010 hosted

Hi,
Out of Office doesn't work today, we get this message:
"
Client Information
------------------
User Agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:31.0) Gecko/20100101 Firefox/31.0
CPU Class: undefined
Platform: Win32
System Language: undefined
User Language: fr-FR
CookieEnabled: true
-----------------
Exception Details
-----------------
Date: Thu Aug 07 2014 14:39:49 GMT+0200
Message: TypeError: $0.GetNewStandaloneEditor is not a function
Url: https://webmail.contoso.fr/ecp/14.2.247.5/Scripts/wizardproperties.js
Line: 175

Call Stack
----------
ErrorHandling.showUnhandledException@https://webmail.contoso.fr/ecp/14.2.247.5/Scripts/common.js:252:1202
Function.createDelegate/<@https://webmail.contoso.fr/ecp/ScriptResource.axd?d=aQoRX1bD4arQGradX-uxnTbbxVz7gNtmLUnnqJsBgmnyd3IV9NGWm6em3rmOM7UwnsvBvpRPw-S9yMWflWIDg8bdlQiqPQgaCFfAj3sURm5Mi061I_hwScphGOkWW3cvIh-a6skx4OHj3l8D0&t=ffffffffb868b5f4:5:298


Detailed Call Stack
-------------------
"

Yesterday we remove 1 server from the dag. I presume it's the cause of the problem but we can't return it.

Can you tell me what is missing on my servers to make this work again?

configuration: 3 server dag exchange 2010 sp2 hosted mode.
out of office work well with outlook client.

Thanks for your help

Regards
Jeremy