Cannot unzip more than 1 file

[charlie]

procedure ExtractImageSet(zipfilename,folder:string; wc:pwc);
var
//Unzipper: TVCLUnZip;
temp: string;
begin
//Unzipper := TVCLUnZip.Create(nil);
if mainwnd <> nil then
begin
with mainwnd.VCLZip1 do
begin
temp := justdirname(inifilename)+folder+zipfilename+'.zip';
ZipName := justdirname(inifilename)+folder+zipfilename+'.zip';
ReadZip;
DoAll := true;
DestDir := justdirname(inifilename)+folder;
RecreateDirs := True;
RetainAttributes := True;
Unzip;
end;
end;
end;

See my code above. For some reason I can unzip a single bmp file but not more than 1 in the same zip. I get EBadZipFile telling me that the zip file is invalid. Why is this? I followed the tutorial and an existing example in our codespace down to a t.