Access Violation Exception

public bool StartOPCConnection()
        {
            bool retval = false;
            // Local variables
            Type svrComponenttyp;

            // initialize output parameters.
            IntPtr pResults = IntPtr.Zero;
            IntPtr pErrors = IntPtr.Zero;
            // Initialise Group properties
            int bActive = 1;
            int dwRequestedUpdateRate = 250;
            int hClientGroup = 0;
            int dwLCID = iLOCALE_ID;
            int pRevUpdateRate;
            int TimeBias = 0;
            float deadband = 0;

            // Access unmanaged COM memory
            GCHandle hTimeBias, hDeadband;

            hTimeBias = GCHandle.Alloc(TimeBias, GCHandleType.Pinned);
            hDeadband = GCHandle.Alloc(deadband, GCHandleType.Pinned);

            // 1. Connect to the local server.
            // Get the Type from the progID and create instance of the OPC Server COM
            // component
            Guid iidRequiredInterface = typeof(IOPCItemMgt).GUID;
            svrComponenttyp = System.Type.GetTypeFromProgID(this.sLOCAL_SERVER);


            try
            {
                pIOPCServer = (IOPCServer)System.Activator.CreateInstance(svrComponenttyp);
                try
                {
                    OPCITEMDEF[] ItemDefArray;
                    /* 2. Add a new group
                        Add a group object and querry for interface IOPCItemMgt
                        Parameter as following:
                        [in] not active, so no OnDataChange callback
                        [in] Request this Update Rate from Server
                        [in] Client Handle, not necessary in this sample
                        [in] No time interval to system UTC time
                        [in] No Deadband, so all data changes are reported
                        [in] Server uses english language to for text values
                        [out] Server handle to identify this group in later calls
                        [out] The answer from Server to the requested Update Rate
                        [in] requested interface type of the group object
                        [out] pointer to the requested interface
                    */
                    pIOPCServer.AddGroup(sGROUP_NAME,
                        bActive,
                        dwRequestedUpdateRate,
                        hClientGroup,
                        hTimeBias.AddrOfPinnedObject(),
                        hDeadband.AddrOfPinnedObject(),
                        dwLCID,
                        out nSvrGroupID,
                        out pRevUpdateRate,
                        ref iidRequiredInterface,
                        out pobjGroup1);

                   
                    // Initialize all IO interface pointers.
                    InitReqIOInterfaces();
                    /* 3. Add items to the group */
                    ItemDefArray = new OPCITEMDEF[uiAMOUNT_OF_ITEMS];
                    for (int iArrayIndex = 0; iArrayIndex < uiAMOUNT_OF_ITEMS; iArrayIndex++)
                    {
                        ItemDefArray[iArrayIndex].szAccessPath = "";             // Accesspath not needed for this sample
                        ItemDefArray[iArrayIndex].szItemID = saItemNames[iArrayIndex];     // ItemID, see above
                        ItemDefArray[iArrayIndex].bActive = 1;              // item is active
                        ItemDefArray[iArrayIndex].hClient = iArrayIndex;              // client handle
                        ItemDefArray[iArrayIndex].dwBlobSize = 0;              // blob size
                        ItemDefArray[iArrayIndex].pBlob = IntPtr.Zero;    // pointer to blob
                        ItemDefArray[iArrayIndex].vtRequestedDataType = 6;              // set real as datatype 
                    }


                    try
                    {
                        OPCITEMDEF[] tempItemDefArray = new OPCITEMDEF[uiAMOUNT_OF_ITEMS];

                        for (int idx = 0; idx < uiAMOUNT_OF_ITEMS; idx++)
                        {
                            tempItemDefArray[idx] = ItemDefArray[idx];
                        }


                        // Add items to group
                        lock ((IOPCItemMgt)pobjGroup1)
                        {
                            ((IOPCItemMgt)pobjGroup1).AddItems(uiAMOUNT_OF_ITEMS, tempItemDefArray, out pResults, out pErrors);
                        }
                        // Unmarshal to get the server handles out fom the m_pItemResult
                        ItemSvrHandleArray = new int[uiAMOUNT_OF_ITEMS];

                        // after checking the errors
                        int[] errors = new int[uiAMOUNT_OF_ITEMS];
                        IntPtr pos = pResults;

                        Marshal.Copy(pErrors, errors, 0, uiAMOUNT_OF_ITEMS);

                        for (int idx = 0; idx < uiAMOUNT_OF_ITEMS; idx++)
                        {
                            if (errors[idx] == 0)
                            {
                                OPCITEMRESULT[] result = new OPCITEMRESULT[uiAMOUNT_OF_ITEMS];

                                result[idx] = new OPCITEMRESULT();
                                result[idx] = (OPCITEMRESULT)Marshal.PtrToStructure(pos, typeof(OPCITEMRESULT));
                                pos += Marshal.SizeOf(typeof(OPCITEMRESULT));

                                ItemSvrHandleArray[idx] = result[idx].hServer;
                                //Set returnvalue to true, because startup went OK
                                retval = true;
                            }
                            else
                            {
                                pIOPCServer.GetErrorString(errors[idx], iLOCALE_ID, out sErrors[idx]);
                                retval = false;
                            }

                        }
                        // Destroy indirect structure elements
                        Marshal.DestroyStructure(pos, typeof(OPCITEMRESULT));

                    }
                    catch (AccessViolationException error) // catch for error in adding items.
                    {
                        lc.AddLog(LoggingState.EXCEPTION, error.ToString());
                        retval = false;
                    }
                  
                }
                catch (System.Exception error) // catch for error in creation group
                {
                    lc.AddLog(LoggingState.EXCEPTION, error.ToString());
                    retval = false;
                }
                finally
                {
                    if (hDeadband.IsAllocated) hDeadband.Free();
                    if (hTimeBias.IsAllocated) hTimeBias.Free();
                }

            }
            catch (System.Exception error) // catch for error in creating server
            {
                lc.AddLog(LoggingState.EXCEPTION, error.ToString());
                retval = false;
            }
            return retval;
        }//End StartOPCConnection()