PTC Solutions Installer (PSI) for Windchill 10.x fails with error message "Windchill Loader failed!" and "Installation is Aborting“.

• PTC Solutions Installer (PSI) fails with error message Windchill Loader failed! and Installation is Aborting.  The installation cannot continue. in the PTCSOLNINSTALLER_PtcInstall.log
• The full error as seen in the PTCSOLNINSTALLER_PtcInstall.log:

DEBUG  <date> - Exception while attempting to connect (web service may simply not be running)java.net.ConnectException: Connection refused
 at java.net.PlainSocketImpl.socketConnect(Native Method)
 at java.net.PlainSocketImpl.doConnect(PlainSocketImpl.java:351)
 at java.net.PlainSocketImpl.connectToAddress(PlainSocketImpl.java:213)
 at java.net.PlainSocketImpl.connect(PlainSocketImpl.java:200)
 at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:366)
 at java.net.Socket.connect(Socket.java:529)
 at sun.net.NetworkClient.doConnect(NetworkClient.java:158)
 at sun.net.www.http.HttpClient.openServer(HttpClient.java:394)
 at sun.net.www.http.HttpClient.openServer(HttpClient.java:529)
 at sun.net.www.http.HttpClient.<init>(HttpClient.java:233)
 at sun.net.www.http.HttpClient.New(HttpClient.java:306)
 at sun.net.www.http.HttpClient.New(HttpClient.java:323)
 at sun.net.www.protocol.http.HttpURLConnection.getNewHttpClient(HttpURLConnection.java:970)
 at sun.net.www.protocol.http.HttpURLConnection.plainConnect(HttpURLConnection.java:911)
 at sun.net.www.protocol.http.HttpURLConnection.connect(HttpURLConnection.java:836)
 at com.ptc.windchill.install.suite.runnables.AbstractWebService.attemptConnect(AbstractWebService.java:228)
 at com.ptc.windchill.install.suite.runnables.AbstractWebService.isRunning(AbstractWebService.java:201)
 at com.ptc.windchill.install.suite.runnables.AbstractWebService.start(AbstractWebService.java:295)
 at com.ptc.windchill.install.suite.WindchillLoaderManagerImpl.startApache(WindchillLoaderManagerImpl.java:488)
 at com.ptc.windchill.install.suite.WindchillLoaderManagerImpl.loadSubinstallerData(WindchillLoaderManagerImpl.java:134)
 at com.ptc.windchill.install.suite.WindchillLoaderManagerImpl.process(WindchillLoaderManagerImpl.java:87)
 at com.ptc.windchill.install.suite.WindchillLoaderManager.process(WindchillLoaderManager.java:29)
 at com.ptc.windchill.install.framework.InstallAction.run(InstallAction.java:463)
 at com.ptc.windchill.install.framework.InstallAction.install(InstallAction.java:310)
 at com.zerog.ia.installer.actions.CustomAction.installSelf(DashoA10*..)
 at com.zerog.ia.installer.InstallablePiece.install(DashoA10*..)
 at com.zerog.ia.installer.InstallablePiece.install(DashoA10*..)
 at com.zerog.ia.installer.InstallablePiece.install(DashoA10*..)
 at com.zerog.ia.installer.InstallablePiece.install(DashoA10*..)
 at com.zerog.ia.installer.GhostDirectory.install(DashoA10*..)
 at com.zerog.ia.installer.InstallablePiece.install(DashoA10*..)
 at com.zerog.ia.installer.Installer.install(DashoA10*..)
 at com.zerog.ia.installer.actions.InstallProgressAction.n(DashoA10*..)
 at com.zerog.ia.installer.actions.ProgressPanelAction$1.run(DashoA10*..)
DEBUG  <date> - apache appears to be down.  Starting it...
DEBUG  <date> - Starting Apache...
DEBUG  <date> - Executing command: /ptc/Apache/bin/apachectl -k start
DEBUG  <date> - Executing: /ptc/Apache/bin/apachectl -k start
DEBUG  <date> - socket connect to localhost:<port> completed with no error
DEBUG  <date> - Checking if web service is running...
DEBUG  <date> - checking URL connection to http://<hostname>:<port>  ...
DEBUG  <date> - apache running at http://<hostname>:<port>
DEBUG  <date> - Apache seems to be running.
INFO   <date> - Loader command: /ptc/Windchill/bin/windchill --java=/ptc/Java/bin/java --javaargs=-Dwt.load.installer.serverManagerTimeout=300 wt.load.WindchillLoader -All -Unattended -AbortOnError -Locale=en -User=<user> -Password=<password>
INFO   <date> - joining with std out thread
INFO   <date> - std out join complete.
INFO   <date> - joining with std error thread
INFO   <date> - std err join complete.
FATAL  <date> - Windchill loader exited with error status = 1
DEBUG  <date> - Installation is Aborting.  The installation cannot continue.
DEBUG  <date> - Installation is Aborting.  The installation cannot continue.