And until such time that fire can melt metal, there never will be.;)
As with all networked computer systems, the security is comprised of 3 things: initial setup (including o/s and software install), physical security of the machines and isolation of the network. Excepting a breech of one of the above, the Diebold system is fine. In my 20+ years working with computer systems, I've found most security breeches involve stupidity or laziness on some level or another.
Bottom line: computerized voting machines make it easier to vote and much, MUCH harder for the average person to 'fix' an election.