He did not say he doesn’t know much about the subject, just that it is one area that he would like to know better, and it was in a wide ranging interview on the fact that he wants to surround himself with good advisers, and not yes men:

http://weblogs.baltimoresun.com/news/politics/blog/2007/12/mccain_he_wants_people_to_tell.html
"The issue of economics is something that I’ve really never understood as well as I should. I understand the basics, the fundamentals, the vision, all that kind of stuff,” he said. "But I would like to have someone I’m close to that really is a good strong economist. As long as Alan Greenspan is around I would certainly use him for advice and counsel."

McCain said his staff hates it when he discusses his shortcomings on economics, even though he has read widely and studied the subject.

His economic vision - less government, less spending, less taxes - still sound much better to me than Clinton’s & Obama’s knee jerk reaction to the credit issue - government bailout, government regulation, create new government bureaucracies.    And I think I would put his knowledge of economics up against theirs any day. 

I do not want to live in a nanny state.  I want free markets to figure this out, and they do.  We had "irrational exuberance" in the stock market in the late ’90’s which led to short term economic crisis & correction in early part of this decade, and this credit crunch will pass too - and hopefully in the process will flush a few financial institutions that were getting too fancy with their "financial instruments" and risk taking down the toilet.  Prosecution if any of them broke laws by hiding the risks they were taking.  That is a "market correction" that has some lasting impact - shareholders will demand better protections from the surviving institutions, and punish them with low stock prices - just as they did to Enron and other firms that even smelled like Enron after the stock bubble burst.