InternetReadFile returns additional characters at the end when reading several b

I have the following problem: I am using wininet's InternetReadFile to
read an XML file from a server (find the code snippet below). I have
set a BLOCK_SIZE of 512 bytes to read with each InternetReadFile call.
Sometimes the XML which is read into my lpBuffer looks wellformed, but
sometimes I can see at the end of the file some additional characters,
e.g. if my XML would look correctly like this:

...
</Inspection>
</Task>
0

I sometimes see this:

...
</Inspection>
</Task>ction>
</Task>
0

So it looks like some memory problem and that the buffer is not filled
up correctly? Anyhow if I set the BLOCK_SIZE to 1 then I don't get this
effect anymore, actually I will receive the following result:

...
</Inspection>
</Task>

So here my last character '0' is missing. Does anyone have an
explanation why I have this effect when reading several bytes with
InternetReadFile? How can I solve this problem if I don't want to read
each byte by byte (if I do so my last byte doesn't get read anymore)?
Thanks a lot for any suggestions!

Peter


Here's my code snippet (remark: m_hHttpOpenRequest is the handle
returned by 'HttpOpenRequest'):


BOOL CTest::ReadStream()
{
   int BLOCK_SIZE = 512;

   DWORD dwBufferLen;
   DWORD dwSize = sizeof(DWORD);
   if (HttpQueryInfo(m_hHttpOpenRequest, HTTP_QUERY_CONTENT_LENGTH |
HTTP_QUERY_FLAG_NUMBER,
      &dwBufferLen, &dwSize, 0))
   {
      dwBufferLen = dwBufferLen + 1; // the content-length does not
include the '\0' byte!
   }


   BYTE* lpBuffer = new BYTE[dwBufferLen];
   memset(lpBuffer, 0, dwBufferLen);

   BYTE *p = lpBuffer;
   DWORD dwRemainingBytes, dwBytesToRead;
   DWORD dwBytesRead = 1;
   while (dwBytesRead > 0)
   {
      dwRemainingBytes = dwBufferLen - (p - lpBuffer);
      dwBytesToRead = min(BLOCK_SIZE, dwRemainingBytes);

      if (!InternetReadFile(m_hHttpOpenRequest, (LPVOID)p,
dwBytesToRead, &dwBytesRead))
      {
         return FALSE;
      }

      p += dwBytesRead;
   }

   return TRUE;
}