Are you by any chance using the 10.2.2 versions? If so, read the technote below then try the following:
Uninstall all versions of Cognos for MS Office and CAFE if they exist
Install CAFE 10.2.2
Patch CAFE with FP2 - http://www-01.ibm.com/support/docview.wss?uid=swg24038880
Install Cognos for MS Office 10.2.2
Don't patch Cognos for MS Office.
No I am using the 10.2.0 version of Cognos and MS Office 2007. I had MS Office 2010 but when the problems started with the installation Cognos for MS Office, I first thought that the version is not supported and reinstall the previous version 2007.
I tried to do what you advise me. First installed CAFE and then Cognos for MS Office. Now there is no connection to the server and the following error:
System.Collections.Generic.KeyNotFoundException: The given key was not present in the dictionary.
at System.Collections.Generic.Dictionary`2.get_Item(TKey key)