Git Submodule checkout hanging

Hi,

I have configured my git repository with SSH-key authentication. My repository has a reference to a submodule, so I have checked the "Use submodules" flag in the checkout task configuration.
The .gitmodule config does not have a username set in the URL:
[submodule "submodule/sub1"]
path = submodule/sub1
url = ssh://xxxx/git/xxxxxxxxx

When bamboo runs the ""C:\Program Files (x86)\Git\bin\git.exe" submodule update --init --recursive" command, my build hangs at the log output:

21-May-2013 18:42:14 Submodule 'submodule/sub1' (ssh://xxxxx/git/xxx/xxx) registered for path 'submodule/sub1'
21-May-2013 18:42:15 Cloning into 'submodule/sub1'...

Even a "stop currently running build" does not stop the build.
21-May-2013 19:00:33 Request to stop 'XXXXXXXXX' received from xxxxxxxx

I have to kill the agent process in order to stop the build.

I have downloaded the newest git version (https://code.google.com/p/msysgit/downloads/list?can=3&q=official+Git) described here: https://confluence.atlassian.com/display/BAMBOO/Git
I have created a Git capability pointing to "C:\Program Files (x86)\Git\bin\git.exe".

Maybe git is hanging at a password prompt?
Why does it not hand over the ssh authentication properly?

Any advice?
Thanks,
Martin