The computerized voting machines used by many voters in the 23rd district had a computer virus - tainting the results, not just from those machines known to have been infected, but casting doubt on the accuracy of counts retrieved from any of the machines.
Of further note, the models of ImageCast machines used in the districts have a slot through which the paper ballot is deposited into a secure holding tank underneath the machine after the ballot is scanned by the machine. The problem is that the slot is readily accessible to the voter (or poll worker) to stuff manually. 10 voted ballots could be deposited in the slot for every one voter... and if the electronic count was compromised, the "paper backup" would be useless.
The ImageCast machines have one more significant and scary flaw: USB ports. USB ports allow various devices to be attached to a computer in order to input information, connect a device, add wireless network capability and so on. Wireless network devices and USB storage devices can (and are) made small enough to fit into a regular wristwatch or bracelet.