Applies To:
  • CitectSCADA 3.00

After upgrading from Citect version 3.30 to 3.40 and after a few minutes an error message box popped up on the I/O Server with the following:

File (i:\cit34_42\source\display\netb.c) Line (254)
Error NCB did not cancel 48ef005c

This was also recorded in the SYSLOG.DAT file. While this message box was on the screen, the I/O Server stopped processing incoming messages from the clients and the control system was effectively halted. After the OK button was pressed, the system seemed to continue as normal and processed what appeared to be buffered messages.


CIT has confirmed this to be a problem in Citect for Windows version 3.40. We are researching this problem and will post new information here as it becomes available.

This error is associated with Citect's client/server communication and so will only occur when using Citect over a network. Single standalone Citect installations will not report this error. This error will occur under some yet unknown network conditions. This is most likely when the connection between the Citect client and the Citect server will be closed under an error condition. This could happen in highly loaded LAN's or WAN's with unreliable or slow connections. We are still investigating this problem and will post an alert when a solution is known.

A possible work around includes setting the following parameter:


If this parameter does not resolve the problem then try setting:


If this does not solve the problem then go back to Version 3.30 or use the 32 bit version 4.20. This problem has been solved in Citect version 3.40/4.20 Service Pack D