ReadFile API for USB device

Hi,
This is my first app for USB device and I am really struggling.
I am using Microsoft Device Simulation Framework and winDDK package to test my app.
My app simply writes data to a file (USB pipe) and reads from it – simple HDLC protocol.
I am running my app on windows 7 64 bit version, but the app is compiled as 32 bit version.

I am using USB handle with the OVERLAPPED structure – in other words non-blocking code (provided below).
My problem is that if I call ReadFile with RxSize set to 1024 the function just does not read anything – GetOverlappedResult always returns false and my RxCount is 0 – so no data has been received.
If I use nNumberOfBytesToRead set to 256 bytes it works like charm. I have also checked MaximumPacketSize of the USB_ENDPOINT_DESCRIPTOR
Structure and it says 1024.
I hope that maybe somebody else has come across the same issue and might have some solution.

Regards,
Janusz
Code;

Code:

// ---------------------------------------------------------- // Name: Receive // Description: Read RX data from the port // Inputs: RxSize - Size of storage for receiving // Outputs: RxBuffer - The storage // Returns: Number of data bytes received // ---------------------------------------------------------- int UsbAccess::Receive (UCHAR *RxBuffer, int RxSize) { DWORD ErrorFlags; DWORD RxCount = 0; OVERLAPPED gOverlapped; HANDLE event; DWORD dwError; DWORD nBytesRead; // set up overlapped structure fields gOverlapped.Offset = 0/*offset*/; gOverlapped.OffsetHigh = 0; gOverlapped.hEvent = CreateEvent(NULL, TRUE, FALSE, NULL); DWORD test = ::GetLastError(); BOOL bResult = ReadFile (hRead, RxBuffer, RxSize, &RxCount, &gOverlapped); // if there was a problem, or the async. operation is still pending. if (!bResult) { // deal with the error code switch (dwError = GetLastError()) { case ERROR_HANDLE_EOF: { // we have reached the end of the file // during the call to ReadFile // code to handle that } case ERROR_IO_PENDING: { // asynchronous i/o is still in progress // do something else for a while WaitForSingleObject(gOverlapped.hEvent, 1000); nBytesRead = 0; // check on the results of the asynchronous read bResult = GetOverlappedResult(hRead, &gOverlapped, &nBytesRead, FALSE) ; // if there was a problem ... if (!bResult) { // deal with the error code switch (dwError = GetLastError()) { case ERROR_HANDLE_EOF: { // we have reached the end of // the file during asynchronous // operation } // deal with other error cases } //end switch (dwError = GetLastError()) BOOL result = CancelIo(hRead); offset = 0; // check on the results of the asynchronous read bResult = GetOverlappedResult(hRead, &gOverlapped, &nBytesRead, TRUE) ; if(GetLastError() == ERROR_OPERATION_ABORTED) { nBytesRead = 0; } } else { offset += nBytesRead; cout << "Got data"; } return nBytesRead; } // end case // deal with other error cases, such as the default } // end switch (dwError = GetLastError()) } // end if CloseHandle(gOverlapped.hEvent); test = ::GetLastError(); return (RxCount); }