The .NET Reflector free version is no more available on Red Gate site. I uploaded free versions on megaupload. Each version requires to update if it’s too old. To get it working without updating, you must go back with system time.
The links are these:
.NET Reflector 6.8.2.5 (no updates on 16/09/2011)
.NET Reflector 6.5.0.135 (no updates on 20/02/2010)