If this is IS7.1, then I would recommend using wm-isclient.jar from the patch IS_7.1.2_CL_Fix7. I have seen a problem whereby a Java client calls an IS which runs successfully but the connection is not really properly closed and kept alive which means the Java client program never ends. Using wm-isclient.jar from this patch fixes that problem. So I would recommend doing this anyway regardless.
If that doesn’t fix the problem then you will probably need to raise a support incident via empower.softwareag.com.
#webMethods#Integration-Server-and-ESB