My way would be as follows:
1. Stop any BEWS services on that server in question.
2. Delete any directories that the RAWS agent was installed into.
3. Get hold of Microsoft's MSI Installer Cleanup Utility and run it, and select the option to delete entries for RAWS. Make sure you backup your registry first.
4. Run the install of the 11D agent again.
By the way, have you tried to update this manually by browsing to your installation folder and running it from there?