Have you tried downloading all the packages (SIMPL, DeviceDB, etc) individually, then disconnect from the internet, and install the software that way?? For SIMPL, you may need to download and install Net Frameworks Compact 3.5 from Microsoft before hand if it is not already installed on your computer.? The order you install Crestron software is important.? Start with the databases and end with SIMPL & VTPRO.
