error loading messages from message queue

hi,

i got a little problem with loading messages from a message queue.

my config:
jtopen 4.0
java 1.3.1 (on both iSeries and PC, both from IBM)
iSeries 890 with OS/400 V5R2

i'm trying to read all messages from a message queue. i got no problem
running my programm on my pc. works all fine there. but then i tried it
on the iSeries and ... and it doesn't work. the error message comes on
the load method of the MessageQueue object.

java.lang.NoClassDefFoundError: com/ibm/as400/system/UnixSocket
java/lang/Throwable.<init>(Ljava/lang/String;)V+4 (Throwable.java:90)
java/lang/Error.<init>(Ljava/lang/String;)V+1 (Error.java:46)
java/lang/LinkageError.<init>(Ljava/lang/String;)V+1
(LinkageError.java:39)
java/lang/NoClassDefFoundError.<init>(Ljava/lang/String;)V+1
(NoClassDefFoundError.java:43)
com/ibm/as400/access/SocketContainerUnix.setServiceName(Ljava/lang/Strin
g;)V+0 (SocketContainerUnix.java:54)
com/ibm/as400/access/PortMapper.getServerSocket(Ljava/lang/String;ILcom/
ibm/as400/access/SSLOptions;)Lcom/ibm/as400/access/
SocketContainer;+0 (:??)
com/ibm/as400/access/AS400ImplRemote.signonConnect()V+0
(AS400ImplRemote.java:1573)
com/ibm/as400/access/AS400ImplRemote.signon(Ljava/lang/String;Ljava/lang
/String;[BI)Lcom/ibm/as400/access/SignonInfo;+0 (AS
400ImplRemote.java:1445)
com/ibm/as400/access/AS400.sendSignonRequest()V+0 (AS400.java:2373)
com/ibm/as400/access/AS400.signon(Z)V+0 (AS400.java:2854)
com/ibm/as400/access/AS400.getCcsid()I+0 (AS400.java:936)
com/ibm/as400/access/MessageQueue.load()V+0 (:??)
org/porta/message/MessageQueueListener.run()V+0
(MessageQueueListener.java:57)

any suggestions?