Hallo Sascha,
meinst Du eine neue I5 ?

Vielleicht hiflt Dir dies ?

Corrections in V5R3 Might Cause Problems with SNA Server
Incident Summary

Problem Summary:
Microsoft SNA Server, now branded Host Integration Server, might encounter problems when used with IBM eServer™ i5 servers at V5R3 of IBM i5/OS™. A problem that exists in previous versions of IBM OS/400 was corrected in V5R3 and it appears that the SNA Server was exploiting this problem or treating it as though the incorrect behavior were by design. The errors that the user receives can vary. It usually surfaces as a file in use or an authority type error to the client PC.

Resolution:
Because some old client products were relying on this working as it had, IBM has decided to allow this technically incorrect behavior to continue but only for the old file server data stream that this client uses. APAR SE19221 addresses this change. The resulting PTF, SI17590, returns the behavior of the file server to the way it worked prior to V5R3.

References:
For additional information, refer to the following APAR:

APAR SE19221: