Microsoft released update rollup 5 for Microsoft Dynamics CRM 2011 on 20th October 2011 (KB 2567454).

You can download it at the following location,

http://www.microsoft.com/download/en/details.aspx?displaylang=en&id=27820

The KB article contains the installation instructions and list of fixes.

http://support.microsoft.com/kb/2567454

Note you can't remove rollup 5 once it has been installed.