In order to resolve this, we need to determine whether the problem is in the server or in the client, and therefore get a capture of the communication between them. For this, please download and install the <a href="/LinkClick.aspx?fileticket=7Cz9jlnFyho%3d&tabid=195">OPC Analyzer Tool (<a href="/LinkClick.aspx?fileticket=E3G2uWvIhrw%3d&tabid=195">readme file).
After installing, enter any necessary information in the "Category Filter" and "Remote Machine Name" fields, and press the "Refresh" button. Then, select your target OPC server from the "Server" drop-down, and make sure the trace is started (if "TRACE STOPPED" is displayed, press the "start trace" button).
You then need to modify your application (or change the settings in the demo app) to connect to the OPC Analyzer instead of your real target OPC server; the OPC Analyzer acts as an intermediate logger. The ProgID of the OPC Analyzer is "OpcTestLab.OpcAnalyzer.1". You can then run your application, and you should see the trace being collected in the OPC analyzer. It might be helpful to make handnotes of times of any relevant events, such as the time when you have started the application, and when the exception occurred. Afer you are finished, select File -> Save Trace in the Opc Analyzer, save the .TRA file, and send it to us - ideally, attach it to your reply in this forum.
Note: The OPC Analyzer tool is available to OPC corporate members only (such as OPC Labs are), thus the download is only permitted to your user account (you must be logged into our site), and you can only use it for the purpose of troubleshooting this particular problem.

Thank you. I understand that your problem is not resolved, but actually this result is positive, because it shows that the original bug is resolved. There must be a separate reason for this new problem.
Can you please let me know:

Does this error happen only after you "read" or "subscribe", or does some problem also happen when you try to browse for items inside the server?
Have you tried it with the server and client on the same machine? If so, what was the result?
Is the (trial version of the) server available? If you do not know where I can obtain it, I will ask the manufacturer.

Note: do not use OPCItemGen for any further tests; either use your application, or the demo app (as you are doing), etc., just not OPCItemGen - it has a separate codebase which is not yet updated.

Thank you.
I was finally able to reproduce the problem, or something similar. Fix for this is ready.
The new build is available from the Downloads page. Verification: It is labeled 5.11.482.1 or later.

There is just a single QuickOPC-Classic 5.11 on that page. You cannot make a mistake. Ignore the modification date listed.

The new build is available from the Downloads page. Verification: It is labeled 5.11.481.1 or later.