John,

I had a similar problem a while back and came across this fix.
Just add the following unit to your project.

unit D7ComboBoxStringsGetPatch;

// The patch fixes TCustomComboBoxStrings.Get method for empty string item
in Delphi 7.

interface

{$IF RTLVersion <> 15.0}
'This patch is intended for Delphi 7 only';
{$IFEND}

implementation

uses
Windows, SysUtils, StdCtrls;

resourcestring
RsPatchingFailed = 'TCustomComboBoxStrings.Get patching failed.';

type
TPatchResult = (prNotNeeded, prOk, prError);

function PatchCode(RoutineStartAddr: Pointer; PatchOffset: Cardinal;
OriginalCode: Pointer;
OriginalCodeLen: Cardinal; PatchedCode: Pointer; PatchedCodeLen:
Cardinal): TPatchResult;
const
JmpOpCode = $25FF;
type
PPackageThunk = ^TPackageThunk;
TPackageThunk = packed record
JmpInstruction: Word;
JmpAddress: PPointer;
end;
var
CodeStart: Pointer;
BytesWritten: DWORD;
begin
if FindClassHInstance(System.TObject) <> HInstance then
with PPackageThunk(RoutineStartAddr)^ do
if JmpInstruction = JmpOpCode then
RoutineStartAddr := JmpAddress^
else
begin
Result := prError;
Exit;
end;
CodeStart := Pointer(LongWord(RoutineStartAddr) + PatchOffset);
if CompareMem(CodeStart, OriginalCode, OriginalCodeLen) then
begin
if WriteProcessMemory(GetCurrentProcess, CodeStart, PatchedCode,
PatchedCodeLen, BytesWritten) and
(BytesWritten = PatchedCodeLen) then
begin
FlushInstructionCache(GetCurrentProcess, CodeStart, PatchedCodeLen);
Result := prOk;
end
else
Result := prError;
end
else
Result := prNotNeeded;
end;

type
TCustomComboBoxStringsHack = class(TCustomComboBoxStrings);

function AddrOfTCustomComboBoxStringsGet: Pointer;
begin
Result := @...;
end;

procedure PatchTCustomComboBoxStringsGet;
const
OriginalCode: Cardinal = $74FFF883; // CMP EAX, -1 | JZ +$26
PatchedCode: Cardinal = $7E00F883; // CMP EAX, 0 | JLE +$26
PatchOffset = $1F;
var
PatchResult: TPatchResult;
begin
PatchResult := PatchCode(AddrOfTCustomComboBoxStringsGet, PatchOffset,
@OriginalCode, SizeOf(OriginalCode),
@PatchedCode, SizeOf(PatchedCode));
case PatchResult of
prError:
begin
if IsConsole then
WriteLn(ErrOutput, RsPatchingFailed)
else
MessageBox(0, PChar(RsPatchingFailed), nil, MB_OK or MB_ICONSTOP
or MB_TASKMODAL);
RunError(1);
end;
end;
end;

initialization
PatchTCustomComboBoxStringsGet;

end.