This is a known issue https://issues.jboss.org/browse/JBPM-3279 which was recently resolved.
The visual representation of lanes however is still to be done. With designer version 1.0.0.053 which you can get from sourceforge: http://sourceforge.net/projects/jbpm/files/designer/designer-1.0.0.053/
you can set the lane names in the process properties (see Lanes property. it is a comma-separated list of lane names). Also for any Task node you can also see a Lane property where you can insert the lane name it belings to. Also uploading your existing processes using lanes will work fine.
The visual representation should be done for the next version.