On Thu, 15 Sep 2011 15:46:29 -0400, you wrote: Unless youLre running an NI cluster. If PEDRIVER is loaded shutting the decnet circuit used by it must crash the node. PEDRIVER uses DECnet? I thought that clustering used their own Ethernet packets and that DECnet was merely used for some management functions like SYSMAN. PEDRIVER does NOT use DECnet (Ethertype 0x6003), but a specific SCA protocol (0x6007). If for some reason a NI clustered node looses communication with other cluster members, its activities are temporarily paused and a timer is started; when the timer expires (after RECNXINTERVAL seconds, default 20), the surviving cluster reconfigures itself and goes on without the lost node. Meanwhile, if the lost node reestablishes cluster communications within that interval, everything goes on as before; on the other hand, if the lost node retries to connect after the remaining cluster has reconfigured itself, it receives a sort of negative acknowledge from the cluster connection manager (CNXMAN) and is then forced to crash with a specific CLUEXIT bugcheck code. This is to ensure integrity of the locking database and such. The OP had a different crash (SSRVEXCEPT) which is symptom of a bug, not of a "normal" cluster reconfiguration crash. HTH, :-) G. P.S. The new IPCI interface to PEDRIVER should work in a similar way.