Americablog has a great post up with testimony from a doctor who identifies a number of potential medical problems that McCain may have:
http://www.americablog.com/...
The post is well worth reading. I recommend caution in drawing definitive conclusions - some of the commenters point out difficulties in diagnosis via video - just remember the Bill Frist-Terri Schiavo fiasco - but the problem there is that Frist is not an expert in neurology and so is not qualified to make such a diagnosis in the first place.
The fact that McCain's medical records still are not made available as a public record is unacceptable. Perhaps the campaign knows that there is damning information there that, if released, would end McCain's campaign overnight. But claiming "personal privacy" over medical records for a candidate for president of the United States should not be tolerated.
That McCain has a number of documented episodes of cancer is scary enough, with Palin as VP pick. That he may have undiagnosed, or at least undisclosed, neurological disorders is downright terrifying.