Only executing this particular stored procedure creates this problem. And it only occurs on one server (unfortunately the production server) On all testservers its working just fine.
I've tested already a lot of things. I'm running the code of the stored procedure directly on the database and that works fine. So I'm pretty desperate.
I've solved the problem and want to write down the sollution here too. Maybe its helpfull for somebody.
I call a stored procedure with about 13 parameters from my asp page. I use one in/out parameter, 9 in parameters and 3 out parameters. And the out parameters are the problem. It seems that only 2 out parameters of the type VARCHAR2 or VARIANT are supported. Using more than 2 out parameters of the type varchar2 or variant causes the error ORA-01023: Cursor context not found (Invalid cursor number)
Source: Microsoft OLE DB Provider for Oracle number: -2147467259.
Strangely it only does that on one server.
Now I concatenate two OUT parameters first and later in de code SPLIT them again. This works fine.
Disclaimer: Advice is provided to the best of my knowledge but no implicit or explicit warranties are provided. Since the advisor explicitly encourages testing any and all suggestions on a test non-production environment advisor should not held liable or responsible for any actions taken based on the given advice.