SPARQL update on TDB API frozen at transaction begin

Hi

I'm trying to delete a whole named graph.

The code:
try {
Dataset dataset = TDBFactory.createDataset(directory.getAbsolutePath());
UpdateProcessor qexec = UpdateExecutionFactory.create(request,
GraphStoreFactory.create( dataset ) );
dataset.begin( ReadWrite.WRITE ); // frozen here !!!!!!
qexec.execute();
dataset.commit();

The SPARQL :

WITH <file:/home/jmv/ontologies/unspsc84-title.rdfs.n3>
DELETE { ?subject ?property ?value }
WHERE { ?subject ?property ?value }

The stack when suspending in debugger:

Daemon Thread [SwingWorker-pool-4-thread-1] (Suspended)
Unsafe.park(boolean, long) line: not available [native method]
LockSupport.park(Object) line: 186
Semaphore$FairSync(AbstractQueuedSynchronizer).parkAndCheckInterrupt()
line: 834
Semaphore$FairSync(AbstractQueuedSynchronizer).doAcquireSharedInterruptibly(int)
line: 994
Semaphore$FairSync(AbstractQueuedSynchronizer).acquireSharedInterruptibly(int)
line: 1303
Semaphore.acquire() line: 317
TransactionManager.begin(ReadWrite, String) line: 306
TransactionManager.begin(ReadWrite) line: 287
StoreConnection.begin(ReadWrite) line: 103
DatasetGraphTransaction._begin(ReadWrite) line: 155
DatasetGraphTransaction(DatasetGraphTrackActive).begin(ReadWrite) line: 42
DatasetImpl.begin(ReadWrite) line: 125

Jena:
<dependency>
<groupId>org.apache.jena</groupId>
<artifactId>apache-jena-libs</artifactId><version>2.11.1</version>
<type>pom</type>
</dependency>

The system:
% uname -a
Linux oem-laptop 3.11.0-20-generic #34-Ubuntu SMP Tue Apr 1 20:40:25 UTC
2014 x86_64 x86_64 x86_64 GNU/Linux
% java -version
java version "1.7.0_51"
Java(TM) SE Runtime Environment (build 1.7.0_51-b13)
Java HotSpot(TM) 64-Bit Server VM (build 24.51-b03, mixed mode)

For more details, I'll be on IRC #jena .