From the Washinton Post's Dan Balz:

In addition to major changes in health policy, education policy and energy policy, McCain also envisions fixing Social Security in his first term. There's no doubt that this is one of his goals and his willingness to work across party lines is probably far greater than was Bush's when he undertook his second-term initiative in 2005. But when he says the reforms include "some form of personal retirement accounts," does he mean as part of Social Security -- a non-starter to Democrats -- or separate and apart from Social Security?

I guess we'll have to wait and see.  Remember that McCain supported personal accounts as part of Social Security when he spoke to the Wall Street Journal in March but has since seemed to back away from that position.