Bob,
This is a typical data transmission error. The setup.exe is not complete (similar to a ZIP file where some bytes are missing). Just check the code-signature and you'll find out that it is invalid. This can be caused by an upload and/or download transmission issue.
http://www.lindersoft.com/forums/showthread.php?t=14076
To detect such a transmission error before the installation starts, enable the Archive Integrity option in SetupBuilder.
Friedrich