Have you tried downloading the software again? With a utility like GetRight?
Which version of the software?

The md5sum for the 2.0b13 consumer MkII .upgrade file as I have it here ends in ...fdcc1853b9 .

(Note: I don't use the consumer version, but downloaded it the same time and by the same method as my (functional) developer version (md5sum ends in ....dec1fc773e) )

Any error messages during the installation of the software?

/Michael