Hallo Frank,
ich glaube da besteht ein Problem mit der
QUSRSYS und der Installation der Maschine.
Ich würde vorschlagen einmal ein
chkprdopt 5722SS1 auszuführen und
wahrscheinlich geht dann die Option 1
bzw 3 des Betriebssystem in Error.
Desweiteren gibt es von der IBM ein
Dokument:

Hint and tip

After upgrading to R520 OS/400, clients attempting to use the IBM iSeries Support for Windows Network Neighborhood (NetServer) may be able to locate the NetServer but not map a drive or access the shares. Some versions of Windows may time out after a minute or two and report the following error: Specified network name is no longer available.

Netstat will show the NetServer ports are active and in listen state. No QZLSFILE jobs appear to be started even though they are available in PSRW state. No error messages appear in QSYSOPR. At PTF level MF30129 or later VLOG VL4400000B is logged. Previous PTF levels do not create a VLOG entry.

Traces will show a timeout on the TreeConnect request:
R SessSetup and TreeConnect for a share
... <one minute>
R ECHO
S ECHO
R Disconnect (for the IPC$ logon that worked)
S Disconnect
R FIN ACK
If the trace is allowed to run long enough (5 minutes or so), a reply of error class of 0x02 and an error of 0x0041 may be seen. The problem can occur only on R520 and later of OS/400.

APAR MA26712 added VLOG VL4400000B for this error (errors involving QYSMPUT).

Problem Resolution
The problem occurs when the object QUSRSYS/QYSMSVRE is at an older, incorrect version or is damaged. The most common cause of the problem is an incorrect upgrade or restore of library QUSRSYS.

To recover, delete the user index QUSRSYS/QYSMSVRE, and retry. The object will re-create on first use.

Note: Any customization of subsystem usage for any host server will be lost.

For further information on how to properly restore QUSRSYS, see the Save Restore manual (located in iSeries Information Center). Refer to Chapter 15. Release-to-release support, Previous Release-to-Current Release Support, and Restoring previous release user data to a new system

gruss TARASIK