There is one glaring error in the Constitution, it was the Supreme Court.
The Founding Fathers truly believed that men of honor could only read the Constitution using the words on the document, but only a few short decades after our country was founded, justices began "reading between the lines" for such things as intent. When intent wasn't enough to justify ignoring the words on the page, they moved towards the infamous "living document".
Today, they've moved right past that into the "What the Supreme Court says is law!" And in essence they are right - unless a specific Amendment is passed to allow/disallow a specific law, the Supreme Court is the law of the land - regardless what our Congress decides.
The great error of making the Supreme Court so powerful isn't rooted in the checks and balances, which is an excellent system, but rather the fact that a majority of justices makes a decision. I was recently reminded of the Kelo et al v. City of New London decision - allowing states to take land away from private citizens and give it to other private citizens who promise to increase tax revenues. The decision, like so many BAD decisions, was passed 5 - 4, and there is the glaring error. Four of the most important justices in the land thought the right of a town to forcibly confiscate land from a private homeowner to make way for town homes was blatantly unConstitutional, yet the law was upheld.
How to fix this problem - we need to ask our Congress to begin the process of Amending the Constitution. Like all Amendments it should be short and simple. Here's what I propose:
"Any Supreme Court decision, that is not unanimous, will be construed as a ruling against the government."
Five to four decisions, like Kelo et al v. City of New London, would automatically be victories to the citizens. In situations where a gov't is suing an individual, as in the Bufferd v. Commissioner Of Internal Revenue, anything but a 9-0 decision would rule against the gov't. For reference, the Commissioner of Internal Revenue won that case 9-0.
With many legitimate questions about such things as the "Patriot Act", going to war without a Declaration, and the previously mentioned issue of Eminent Domain - is it so much to ask that the Supreme Court at least be unanimous in approving MORE government power?