HRESULT 80070057 when registering a COM Server from a Windows Service

Hi,

I’ve got an executable that registers a COM server; it can run as an application or as a Windows service, depending on a run time parameter.  When run as an application, other applications can create COM objects that connect to it.  However, I want to run it as a service and to have other applications and other services (on the same machine) create objects that connect to it.

The specific problem: I’m trying to register the COM server with the Windows Running Object Table with grfFlags of (ROTFLAGS_REGISTRATIONKEEPSALIVE | ROTFLAGS_ALLOWANYCLIENT), but I’m getting an HRESULT of 80070057, “One or more arguments are not valid”.

The code below works if the exe is run as an application; but the RunningObjectTable.Register call fails with HRESULT 80070057 when the exe is run as a service.  That leads me to suspect that one of my registry keys/values is not correct for running as a service.  I have tried to set them up according to MSDN page http://msdn.microsoft.com/en-us/library/windows/desktop/ms693774%28v=vs.85%29.aspx, and other nearby pages – details below.  

I’m maintaining a bit of code that has been around for a long time, but I think this is the first time it’s been used to register a COM Server hosted by a windows service.  The code is written using Delphi, but help from anyone familiar with unmanaged calls to these Windows functions would be greatly appreciated!  The target OS is Windows 2012 R2.

The code is:

class function TROT.RegisterActiveObjectEx(Unk: IUnknown; ClassID: TGUID; out Register:Longint): HResult;
var
  Moniker : IMoniker;  
  ClassName: PWideChar;
  RunningObjectTable: IRunningObjectTable;
  PrevUn : IUnknown;
begin
    try
        PrevUnk := RetrieveActiveObjectEx(ClassID);
        if assigned(PrevUnk) then
        begin
            Result := -2; //Ignore duplicate registration
        end
        else
        begin
            ClassName := StringToOleStr(GuidToString(ClassID));
            try
                Result := CreateItemMoniker('!', ClassName, Moniker);

                if Failed(Result) then
                begin
                    exit;
                end
                else
                begin
                    Result := GetRunningObjectTable(0, RunningObjectTable);
                    if Failed(Result) then
                    begin
                        exit;
                    end
                    else
                    begin
                        Result := RunningObjectTable.Register(ROTFLAGS_REGISTRATIONKEEPSALIVE or ROTFLAGS_ALLOWANYCLIENT, Unk, Moniker, Register);
                    end;
                end;
            finally
                SysFreeString(ClassName);
            end;
        end;
    except
        on E:Exception do
        begin
            Result := -1;
        end;
    end;
end;

Registry values set up for the service are given below (HKCR is used to ensure that they are mirrored everywhere required):

[HKEY_CLASSES_ROOT\AppID\Service.exe]
"AppId"="{COM server GUID}"

[HKEY_CLASSES_ROOT\AppID\{COM server GUID}]
"LocalService"="ServiceName"   - as used in a net start command
"AuthenticationLevel"=dword:00000001
"ROTFlags"=dword:00000001

Can anyone help?