Access Violation at address 543848ff in module cgdide50.bpl

I have a class like this
class PACKAGE Ta64 : public TGTIHeader {
public:
   char  Type;
   char  CardNbr[20];
   char  Filler;
   char  Len[3];
   char  Data[650];

   __fastcall Ta64() {
   }

   void __fastcall InitLogOn() {
      Type = 'P';
      Data[3] = 'L';
   }
   void __fastcall InitLogOff() {
      Type = 'P';
      Data[3] = 'O';
   }
   void __fastcall InitStartPurchase() {
      Type = 'P';
      Data[3] = 'P';
   }
   void __fastcall InitEndPurchase() {
      Type = 'P';
      Data[3] = 'E';
   }
   void __fastcall Init() {
AnsiString DateTime;
      memset(locsite, 0x20, sizeof(locsite));
      memcpy(trtype, "a64", 3);
      memset(CardNbr, 0x20, 20);
      Filler = 0x20;
      memset(Len, 0x20, 3);
      memset(Data, 0x20, sizeof(Data));
      DateTime = FormatDateTime("yymmddhhnnss", Now());
      memcpy(&Data[4], DateTime.c_str(), 12);
      memcpy(Len,  "016",3);
      memset(sid, 0x30, 4);
      memset(did, 0x30, 4);
      memset(seqnbr, 0x30, 4);
      memset(retinfo, 0x20, 7);
  }

Quote
}; // sizeof Ta64 = 55 - 705

in code i allocate like this
Ta64 *pa64 = new Ta64
when i delete the object
"delete pa64"
i got this Access Violation at address 543848FF in module cgdide50.bpl Read
of address 00000006
Why?

Thanks for any help
Christer