Examining PE header with mapped file

I have a DLL that maps a file and another DLL that returns information about the mapped file.  The problem is that the function which examines the PE header faults after a few hundred files.  I have not been able to find a handle leak.  Here is the source code:

library ms0001;

{$E dll}
{$R *.res}

uses
  windows;

function tc_openfileview(name: pchar; size: cardinal): pointer; stdcall; export;
var hmap: thandle;
    fh: thandle;
begin
  fh:=createfile(name, GENERIC_READ, FILE_SHARE_READ, nil, OPEN_EXISTING, 0, 0);

  if (fh > 0) then
    begin
      hmap:=createfilemapping(fh, nil, PAGE_READONLY, 0, 0, 'TC_FILE_MAP');
      closehandle(fh);

      if (hmap > 0) then
        result:=mapviewoffile(hmap, FILE_MAP_READ, 0, 0, size)
         else
        result:=nil;
      closehandle(hmap);
    end
     else
    result:=nil;
end;

function tc_closefileview(map: pointer): boolean; stdcall; export;
begin
  result:=unmapviewoffile(map);
end;

exports tc_openfileview, tc_closefileview;

begin
end.


library ms0003;

{$E dll}
{$R *.res}

uses
  windows;

function CheckPEFile(AData:PByte):Boolean; stdcall; export;
//return True if AData points on valid image file
var
 LPNtHdr:PImageNtHeaders;
begin
 Result:=False;
 try
  if PImageDosHeader(AData)^.e_magic<>PWord(PChar('MZ'))^ then Exit;

  LPNtHdr:=Pointer(Cardinal(AData)+Cardinal(PImageDosHeader(AData)^._lfanew));

  if LPNtHdr^.Signature<>PCardinal(PChar('PE'))^ then Exit;       //seems to always fault here

  if LPNtHdr^.FileHeader.Machine<>IMAGE_FILE_MACHINE_I386 then Exit;
  if LPNtHdr^.OptionalHeader.Magic<>IMAGE_NT_OPTIONAL_HDR_MAGIC then Exit;
  Result:=True;
 except
 end;
end;

exports checkpefile;

begin
end.

The main program iterates all files on drive C:\ and passes them to openfileview(filename, 4096) and then uses the returned pointer to pass to CheckPEFile