If you plan to run LiveCycle Workbench on Windows Server 2003 or 2008, you will need to install the Flash Player ActiveX runtime on the server. The browser-based automatic install will not work in most cases.
You can get stand-alone installers for current and older versions of Flash Player here. Download the appropriate Flash Player version and unzip it. The ActiveX plugin installer is named flashplayer10_2<release_number>_winax.exe