In Internet Explorer on the Exchange server, go in to Internet Options, Advanced, and scroll down to Security.
Deselect "Check for Publisher's certificate revocation" and "Check for server certificate revocation". Apply/OK out and then you should find the install goes through in about 40 minutes.
Deselect "Check for Publisher's certificate revocation" and "Check for server certificate revocation". Apply/OK out and then you should find the install goes through in about 40 minutes.
please check this link as well
http://famousphil.com/blog/2010/07/exchange-2010-update-rollup-4-via-windows-updates-dont-do-it/