JBoss WS init fails on Windows when jboss.server.data.dir is a UNC share

When starting JBoss and JBoss-WS on windows with:
run.bat -Djboss.server.data.dir=\\MyMachine\C$\opt\data

Any class annotated @WebService has an auto-generated WSDL whose loading fails with:
ERROR [org.jboss.deployment.MainDeployer] Could not start deployment: file:/opt/jboss/server/default/deploy/nuxeo.ear/platform/nuxeo-platform-5.1.6.jar
org.jboss.ws.metadata.wsdl.WSDLException: java.io.FileNotFoundException: \c$\opt\data\wsdl\nuxeo.ear\nuxeo-platform-5.1.6.jar\NuxeoRemotingService49555.wsdl
at org.jboss.ws.metadata.wsdl.WSDLDefinitionsFactory.getDocument(WSDLDefinitionsFactory.java:198)
at org.jboss.ws.metadata.wsdl.WSDLDefinitionsFactory.parse(WSDLDefinitionsFactory.java:106)
at org.jboss.ws.metadata.ServiceMetaData.getWsdlDefinitions(ServiceMetaData.java:273)
at org.jboss.ws.metadata.ServiceMetaData.eagerInitialize(ServiceMetaData.java:343)
at org.jboss.ws.metadata.UnifiedMetaData.eagerInitialize(UnifiedMetaData.java:147)
at org.jboss.ws.server.ServiceEndpoint.start(ServiceEndpoint.java:106)
at org.jboss.ws.server.ServiceEndpointManager.startServiceEndpoint(ServiceEndpointManager.java:529)
at org.jboss.ws.deployment.ServiceEndpointDeployer.start(ServiceEndpointDeployer.java:144)
at org.jboss.ws.integration.jboss.DeployerInterceptor.start(DeployerInterceptor.java:104)
at org.jboss.deployment.SubDeployerInterceptorSupport$XMBeanInterceptor.start(SubDeployerInterceptorSupport.java:188)
at org.jboss.deployment.SubDeployerInterceptor.invoke(SubDeployerInterceptor.java:95)
at org.jboss.mx.server.Invocation.invoke(Invocation.java:88)
at org.jboss.mx.server.AbstractMBeanInvoker.invoke(AbstractMBeanInvoker.java:264)
at org.jboss.mx.server.MBeanServerImpl.invoke(MBeanServerImpl.java:659)
at org.jboss.mx.util.MBeanProxyExt.invoke(MBeanProxyExt.java:210)
...