Warn message with hazelcast 3.3 while loading mapstoreAll

I am using Hazelcast v3.3. The Hazelcast server runs several map store implementations. I have sporadically seen the following warning in the logs and need to understand what could be causing this and whether it could lead to data loss in the quads. At the moment I have a fairly small cluster to test (4VMs running Ubuntu13 - 2GB RAM each).

2014-09-14 18:55:21,886 WARN c.h.s.i.BasicInvocation [main] [xxx.xxx.xxx.xxx]:5701 [testApp] [3.3] While asking 'is-executing': BasicInvocationFuture{invocation=BasicInvocation{ serviceName='hz:
impl:mapService', op=com.hazelcast.spi.impl.PartitionIteratingOperation@285583d4, partitionId=-1, replicaIndex=0, tryCount=10, tryPauseMillis=300, invokeCount=1, callTimeout=60000, target=Address[xxx.xxx.xxx.xxx]:5701}, done=false} java.util.concurrent.TimeoutException: Call BasicInvocation{ serviceName='hz:impl:mapService', op=com.hazelcast.spi.impl.IsStillExecutingOperation@5b202ff, partit
ionId=-1, replicaIndex=0, tryCount=0, tryPauseMillis=0, invokeCount=1, callTimeout=5000, target=Address[xxx.xxx.xxx.xxx]:5701} encountered a timeout
        at com.hazelcast.spi.impl.BasicInvocationFuture.resolveApplicationResponse(BasicInvocationFuture.java:321)
        at com.hazelcast.spi.impl.BasicInvocationFuture.resolveApplicationResponseOrThrowException(BasicInvocationFuture.java:289)
        at com.hazelcast.spi.impl.BasicInvocationFuture.get(BasicInvocationFuture.java:181)
        at com.hazelcast.spi.impl.BasicInvocationFuture.isOperationExecuting(BasicInvocationFuture.java:390)
        at com.hazelcast.spi.impl.BasicInvocationFuture.waitForResponse(BasicInvocationFuture.java:228)
        at com.hazelcast.spi.impl.BasicInvocationFuture.get(BasicInvocationFuture.java:180)
        at com.hazelcast.spi.impl.BasicInvocationFuture.get(BasicInvocationFuture.java:160)
        at com.hazelcast.spi.impl.BasicOperationService$InvokeOnPartitions.awaitCompletion(BasicOperationService.java:489)
        at com.hazelcast.spi.impl.BasicOperationService$InvokeOnPartitions.invoke(BasicOperationService.java:458)
        at com.hazelcast.spi.impl.BasicOperationService$InvokeOnPartitions.access$600(BasicOperationService.java:430)
        at com.hazelcast.spi.impl.BasicOperationService.invokeOnAllPartitions(BasicOperationService.java:293)
        at com.hazelcast.map.proxy.MapProxySupport.size(MapProxySupport.java:616)
        at com.hazelcast.map.proxy.MapProxyImpl.size(MapProxyImpl.java:72)
        at com.akkadian.wildmetrix.StartHcastServer.main(StartHcastServer.java:105)
        at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
        at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
        at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
        at java.lang.reflect.Method.invoke(Method.java:483)
        at org.eclipse.jdt.internal.jarinjarloader.JarRsrcLoader.main(JarRsrcLoader.java:58)