Problem in connecting to SAP via RFC

Hi all,

I'm running a NON-SAP application on AS/400 (V5R3M0). After connecting successfull to SAP(Kernel 640) via RFC the data exchange is working well, but after app. 1h the connection drops and I get an error in my program. What I've foud out so far, is that the error is raised in module RFC_MT, funktion rfcOpenHooked, line 84. Unfortunaltely this funktion is located in the serviceprogram LIBRFC, so I have got no sourcecode.

The problem raised after upgrading the SAP system to actual version and upgrading the AS/400 to V5R3M0.

I've implemented the actual SDK to my application.

Thanks for help!