this is certainly something d2d should respond to.
that said, lets try a few things:
did you install the game with administrator rights? i.e. did you rightclick on the installer and choose run as administrator?
uninstall the game
download the file again (it is well possible that the download was corrupted in some way)
disconnect from the internet
disable the windows firewall
install the game with admin rights as above
reenable the windows firewall
this may or may not work but would be the first thing I'd try...
if it does not work, please post again