The "Data Execution Prevention" setting in Windows is most likely causing this problem. 

To open the DEP settings:

1. Click on the Start button for Windows.
2. Find Computer on the right side.
3. Right click on Computer and choose Properties.
4. On the left, click on Advanced Settings.  Click Continue/Allow if prompted.
   
5. Under the "Performance" section, click on Settings.
6. Click on the Data Execution Prevention tab.
7. If not chosen already, click on "Allow DEP for all programs and services except those I select:".
8. Continue with the steps below (Excluding Screenwriter 6 from DEP).

Excluding Screenwriter 6 from DEP:

1. Click on the Add button in the DEP window.
2. At the top, under "Look In:" find your hard drive, which is most likely labeled Local Hard Disk (C:) and click on it.
3. On the list of files, find the Program Files (x86) folder and double-click on it.
4. Find the Write Brothers, Inc. folder and double-click on it.
5. Find the Movie Magic Screenwriter 6 folder and double-click on it.
6. Find the file called Scwriter32 and double-click on it.  Movie Magic Screenwriter should now be on the list in the DEP window.
   
7. Click OK twice and try running Movie Magic Screenwriter 6 again by double-clicking on the shortcut on the desktop.
   

There have been extremely rare reports of this issue occurring with a screenshot program called Jing.  Try disabling Jing (or uninstall it) to see if that allows you to use the program.

To disable Jing:

1. Click on Start > All Programs > Accessories > Run (or Start > Run in Windows XP).
2. Type in "msconfig" (without quotes) and click OK.
3. Once the System Configuration Utility comes up, click on the Startup tab.
4. Find the Jing program on the list and uncheck it.
5. Click OK.
6. Restart the computer as prompted.