Following an internal assessment of voting machines used in 2004 and 2006, Colorado Secretary of State Mike Coffman fired off letters to major voting machine vendors informing them that their products had been decertified for use do the detection of serious flaws in their programming that could jeopardize the integrity of the 2008 vote count.
Listed below are the machines decertified and the primary reasons for their disqualification. Note that Precinct Optical Scanner, M100, decertified due to an "inability to complete testing threshold of 10,000 ballots due to vendor programmer errors," is the same model used in every precinct in the state of New Mexico.
Note that the ES&S iVotronic systems were decertified due to "vulnerability to security attack" and "failure to provide audit-able data to detect security violations." The iVotronic was used exclusively on election day 2004 in San Juan County, NM… no other NM County used this equipment. The election day undervote rate in precincts with >50% Native American populations was 5.8%. The election day undervote rate in precincts with >50% Anglo populations was 2.3%.
In addition, Colorado decertified Sequoia Voting Systems (CO Sequoia Decertification.pdf ) for "failure to operate in a secured state requiring passwords" and "failure to provide auditable data to detect security violations." Sequoia Voting systems were used throughout New Mexico during the 2004 election. To see exactly where, check out this link.
To learn more about irregularities in the 2004 election due to e-voting, check out this study of the 2006 elections results, published on Brad Blog.