一个DLL调用ACCESS库的奇怪有关问题(有源码，帮调试下，谢 )

一个DLL调用ACCESS库的奇怪问题(有源码，帮调试下，谢 )
调用DLL，DLL功能就是连接库、打开表，分开调用，也就是一个按钮调用一个函数没有问题，但三个函数合在一个按钮调用就会出错，不知怎么回事？编译没问题，哪个老大帮调试下，谢谢
DLL：
#include <ADODB.hpp>
#include <DB.hpp>
extern "C"__declspec(dllexport) int _stdcall LinkDatabase(TADOConnection *m_AccessConn,String m_DatabaseFile,String m_Pwd="");
extern "C"__declspec(dllexport) bool _stdcall Connection1(TADOConnection *m_AccessConn,TADOQuery *m_Query);

extern "C"__declspec(dllexport) int _stdcall OpenTable(TADOQuery *m_Query,String m_TableName,int m_Flag=0,String m_SQL="");
//=========================
int WINAPI DllEntryPoint(HINSTANCE hinst, unsigned long reason, void* lpReserved)
{
  switch (reason)
  {
  case DLL_PROCESS_ATTACH:
  CoInitialize(NULL);
  break;
  case DLL_PROCESS_DETACH:
  CoUninitialize();
  break;
  case DLL_THREAD_ATTACH: break;
  case DLL_THREAD_DETACH: break;
  default:
  break;
  }
  return 1;
}
//---------------------------------------
int LinkDatabase(TADOConnection *m_AccessConn,String m_DatabaseFile,String m_Pwd)
{
  WideString Link;
  if(m_AccessConn==NULL)
  return -1;
  if(m_DatabaseFile.Trim().Length()==0)
  return -2;
  if(FileGetAttr(m_DatabaseFile) & faReadOnly==faReadOnly)  
  FileSetAttr(m_DatabaseFile,0);
  Link="Provider=Microsoft.Jet.OLEDB.4.0;Data Source="+m_DatabaseFile+";\
  User ID=admin;Jet OleDb:Database Password="+m_Pwd;
  if(m_AccessConn->Connected==false) //如果没有连接到Access
  {
  try
  {
  m_AccessConn->ConnectionString=Link;
  m_AccessConn->LoginPrompt=false;
  m_AccessConn->Connected=true;
  return 0;
  }
  catch(...)
  {
  return -100;
  }
  }
  return -100;
}
//-----------------------------------------
bool Connection1(TADOConnection *m_AccessConn,TADOQuery *m_Query)
{
  if(m_AccessConn==NULL || m_Query==NULL)
  return false;
  m_Query->Connection=m_AccessConn;
  m_AccessConn->Connected=true;
  return true;
}
//-----------------------
int OpenTable(TADOQuery *m_Query,String m_TableName,int m_Flag,String m_SQL)
{
  String m_str;
  if(m_Query==NULL)
  return -1;
  if(m_TableName.Trim().Length()==0)
  return -2;
  m_Query->Close(); m_Query->SQL->Clear();
  switch(m_Flag)
  {
  case 0:
  default:
  m_str="Select * From "+m_TableName;
  break;
  case 1:
  m_str=m_SQL;
  break;
  }
  try
  {
  m_Query->SQL->Add(m_str);
  m_Query->Active=true;
  m_Query->Open();

  }
  catch(...)
  {
  return -100;
  }
  return m_Query->RecordCount;
}
//-----------------------------------------

调用：
HINSTANCE hDLL;
__fastcall TForm1::TForm1(TComponent* Owner)
  : TForm(Owner)
{
  hDLL=LoadLibrary("Database.dll");
}
//----------------------------------------Database.dll-----------------------------------
void __fastcall TForm1::Button1Click(TObject *Sender)//一个按钮连续调用三个函数有问题，但分开三个按钮分别调用就没问题，不知怎么回事？错误提示：EAccessViolation