a DMA PCI Device Driver doesn't work in Vista x64 + 4G RAM platform!!

Hi
  I writed a BDA driver for a PCI TV card device,I found that my driver can
work well on Vista32/XP32/XPx64 + 4G RAM platform, and work well on Vista x64
+ less than 4G RAM, but can't work on Vista x64 + 4G RAM, this problem make
me confused. I guess that this problem maybe result from the DMA addressing
in Vista x64, or MS change the DMA addressing in Vista x64 after XP
x64,so,the DMA configuration of my driver doesn't compatible with Vista x64.
  the following codes is config DMA.

#if defined(_AMD64_)||defined(_IA64_)
 if (Mm64BitPhysicalAddress) //if system support 64-bit physical addressing
 {
  desc.Dma64BitAddresses = TRUE;
  desc.Dma32BitAddresses = FALSE;
  KdPrint(("Mm64BitPhysicalAddress is TRUE \n"));
 }
 else
 {
  desc.Dma32BitAddresses = TRUE;
  desc.Dma64BitAddresses = FALSE;
  KdPrint(("Mm64BitPhysicalAddress is FALSE \n"));
 }
#else
 desc.Dma64BitAddresses = FALSE;
 desc.Dma32BitAddresses = TRUE;
#endif
 desc.AutoInitialize = FALSE;
 desc.MaximumLength = (ULONG) -1;
 m_MaxMapRegisters = (desc.MaximumLength / PAGE_SIZE) + 1;
 m_pDMAObject = IoGetDmaAdapter( pKSDevice->PhysicalDeviceObject,
  &desc,
  &m_MaxMapRegisters);
 m_MaxMapRegisters=(TABLE_SIZE)/8;
    KdPrint(("DMA MaxMap Cnt=%d\n",m_MaxMapRegisters));
 if(!m_pDMAObject)
 {
  KdPrint(("@@@Couldn't GetDMA adapter resource!\n"));
  CleanUpResources();
  return STATUS_INSUFFICIENT_RESOURCES;
 }
 ////Allocate DMA Table memory!
 for(index=0;index<DMA_INT_CNT;index++)
 {
  m_DMAPara[index].KsDMA_Table_VA=(PULONG)(m_pDMAObject->DmaOperations)->
   AllocateCommonBuffer(m_pDMAObject,
   TABLE_SIZE,
   &m_DMAPara[index].KsDMA_Table_PA,
   FALSE);
  if(!m_DMAPara[index].KsDMA_Table_VA)
  {
   KdPrint(("@@@Allocate DMA%d Table Fail!\n",index));
   CleanUpResources();
   return STATUS_INSUFFICIENT_RESOURCES;
  }
  m_DMAPara[index].KsdwDMATableSize=TABLE_SIZE;
 }

 can you give me an idea?

 thanks

 best regards