This is caused by a missing space when using the _topDir parameter. More details can be found here: https://bugs.launchpad.net/ubuntu/intrepid/+source/ant/+bug/296409 This problem occurs on my Ubuntu system
Fix applied using the description. (svn revision 742061, http://svn.apache.org/viewvc?rev=742061&view=rev )
*** Bug 45316 has been marked as a duplicate of this bug. ***