Something must have gone wrong on your system. Our digital signature certificate hasn't been revoked and is valid until October 2010.
Such error message, might indicate that the file you downloaded was altered after it landed on your computer. The whole point of digitally signing executables, is to ensure the version you are trying to run is the same we released, and wasn't altered in any way.
So, either the download didn't go well, in this case you might try download it again (not everything: just one file, for testing), but before download again, clear your Browser cache, otherwise you'll getting the same corrupted file over and over.
