Windows Communication Foundation playback times out

The trace-robotic.log file shows log messages similar to those in the following example:

java.lang.RuntimeException: java.lang.NullPointerException
at com.ibm.rational.test.lt.models.wscore.transport.dotnet.impl.DotNetController
.<init>(DotNetController.java:81)     
at com.ibm.rational.test.lt.models.wscore.transport.dotnet.impl
.DotNetCommunication.<init>(DotNetCommunication.java:75)     
at com.ibm.rational.test.lt.models.wscore.transport.dotnet.impl.DotNetFactoryImpl
.createDotNetComunication(DotNetFactoryImpl.java:22)     
atcom.ibm.rational.test.lt.models.wscore.transport.impl.DotNETTransporterImpl
.send(DotNETTransporterImpl.java:111)     
at com.ibm.rational.test.lt.execution.ws.container.WebServicesMessage
.execute(WebServicesMessage.java:702)     
at com.ibm.rational.test.lt.kernel.action.impl.KAction
.executeAction(KAction.java:484)     
at com.ibm.rational.test.lt.kernel.action.impl.KAction.run(KAction.java:1830)     
at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
at java.lang.Thread.run(Thread.java:781) Caused by: java.lang.NullPointerException
at java.io.File.<init>(File.java:291)     
at com.ibm.rational.test.lt.models.wscore.transport.dotnet.impl.DotNetUtil
.getAbsolutePath(DotNetUtil.java:64)     
at com.ibm.rational.test.lt.models.wscore.transport.dotnet.impl.DotNetProcess
.<init>(DotNetProcess.java:64)     
at com.ibm.rational.test.lt.models.wscore.transport.dotnet.impl.DotNetController
.<init>(DotNetController.java:73)     
... 9 more