Runtime error! - pure virtual function call

Hi, If I work with Axapta COM Connector from C# I get the Runtime Error R6025. My Program Code: AxaptaCOMConnector.IAxapta2 ax2 = new AxaptaCOMConnector.Axapta2Class(); ax2.Logon2(“Admin”,"",“lkv”,"","","",“Axapta25”,"",""); … ax2.Logoff(); ax2 = null; With code between Logon and Logoff it is possible to insert records in the Axapta Database or to select records. But at last I get the RunTime Error R6025. If I comment out all the code between Logon and Logoff I still get the error. Is it the problem with Axapta itself or am I doing something wrong ? What can I do to solve this problem ? Thanks Rakhi.