flexunit task hangs after "Receiving data ..."

Hello,

I am trying to launch the Ant script found in FlexUnit4SampleCIProject but it just doesn't works.

Last message in console is "[flexunit] Receiving data ..." and the tests in the UI are not started and showing 0/100.

I am using latest standalone debug flash player : flashplayer_10.0.42.34_sa_debug.exe

I use flextasks from Flex4 4.0.0.13549 as the flexTasks.jar that comes with the project doesn't work:

BUILD FAILED
X:\wb_fb4\FlexUnit4SampleCIProject\build.xml:47: The class not found in jar file: mxmlc.jar

Buildfile: X:\wb_fb4\FlexUnit4SampleCIProject\build.xml
init:
compile:
    [mxmlc] Loading configuration file F:\Program Files (x86)\Adobe\Adobe Flash Builder Plug-in Beta 2\sdks\4.0.0.13549\frameworks\flex-config.xml
    [mxmlc] X:\wb_fb4\FlexUnit4SampleCIProject\target\bin\Main.swf (469843 bytes)
test:
    [mxmlc] Loading configuration file F:\Program Files (x86)\Adobe\Adobe Flash Builder Plug-in Beta 2\sdks\4.0.0.13549\frameworks\flex-config.xml
    [mxmlc] X:\wb_fb4\FlexUnit4SampleCIProject\target\bin\TestRunner.swf (989770 bytes)
[flexunit] Validating task attributes ...
[flexunit] Generating default values ...
[flexunit] Using default snapshot file path [X:\wb_fb4\FlexUnit4SampleCIProject\target\report\snapshot.jpg]
[flexunit] Using the following settings:
[flexunit]     haltonfailure: [false]
[flexunit]     headless: [false]
[flexunit]     localTrusted: [false]
[flexunit]     player: [flash]
[flexunit]     port: [1024]
[flexunit]     snapshot: [false]
[flexunit]     snapshotFile: [X:\wb_fb4\FlexUnit4SampleCIProject\target\report\snapshot.jpg]
[flexunit]     swf: [X:\wb_fb4\FlexUnit4SampleCIProject\target\bin\TestRunner.swf]
[flexunit]     timeout: [60000ms]
[flexunit]     toDir: [X:\wb_fb4\FlexUnit4SampleCIProject\target\report]
[flexunit]     verbose: [true]
[flexunit]     xcommand: [xvfb]
[flexunit] Setting up server process ...
[flexunit] Starting server ...
[flexunit] OS: [Windows]
[flexunit] Launching player:
[flexunit] Executing 'rundll32' with arguments:
[flexunit] 'url.dll,FileProtocolHandler'
[flexunit] 'X:\wb_fb4\FlexUnit4SampleCIProject\target\bin\TestRunner.swf'
[flexunit] The ' characters around the executable and arguments are
[flexunit] not part of the command.
[flexunit] Opening server socket on port [1024].
[flexunit] Waiting for client connection ...
[flexunit] Client connected.
[flexunit] Setting inbound buffer size to [262144] bytes.
[flexunit] Receiving data ...

Here I can wait long time, and if I close the UI, i get those bonus lines :

[flexunit]
[flexunit] Stopping server ...
[flexunit] End of test data reached, sending acknowledgement to player ...
[flexunit] Closing client connection ...
[flexunit] Closing server on port [1024] ...

BUILD FAILED
X:\wb_fb4\FlexUnit4SampleCIProject\build.xml:68: java.util.concurrent.ExecutionException: java.lang.NullPointerException

Total time: 53 seconds

Am I doing something wrong?

Thank you in advance for your help,

Adnan