The error, "Cannot Connect to SilkTest Workbench. Please make sure it is installed" occurs when executing a SilkTest Workbench script from SilkCentral Test Manager. This error occurs when SCTM is installed before SilkTest Workbench and the machine was not restarted.
If you install SilkCentral Test Manager (SCTM) before SilkTest Workbench, restart your machine after you install SilkTest Workbench. Or, install SilkTest Workbench prior to installing SCTM.