By reinstalling CAS (Client Access Role) I receive:
Another version of this product is already installed. Installation of this version cannot continue. To configure or remote the existing version of this product, use Add/Remove Programs on the Control Panel. Error code is 1638
A few days before I updated the server from rollup 6 to rollup 9.
The version of exchangepackage.msi was older then the Service Pack 1 / rollup installation on the server. I mounted the newest .ISO from “Exchange 2007 SP1 Enterprise ENG” and retry the CAS installation:
Information “exchangeserver.msi” timestamps:
Old exchangeserver.msi:Digital Signature, Timestamp: Tuesday 27 November 2007
New exchangeserver.msi:Digital Signature, Timestamp: Tuesday 6 July 2008
Installation Successful! 🙂