Disc Version Only -

The problem is caused by copy protection the game uses, the first thing to try would be ensure you have the latest patch for Stronghold 2, which is currently at version 1.4.1 available here (external link)

Note to install this patch, you'll need to have updated to 1.4 first, which can be done by downloading the 1.4 patch here (external link)

If the same problem occurs, the next thing would be to ensure you don't have any of following software running:

If you have any of the following programs running in the background, you will have to either disable them or uninstall them. This is because the latest version of the copy protection software (Securom) will refuse to run with the following programs running in the background:

The creators of Securom have created a handy diagnostic tool, which may solve the issue you are having. If the diagnostic tool fails to solve the problem. Please following the instructions on creating a analysis file. Please click here.