JOHANNESBURG (Reuters) - South Africa's rand dipped against the dollar on Tuesday as concerns about the U.S. debt mountain and uncertainty over a bailout for Greece heightened risk aversion. The rand was at 8.7630 to the dollar at 0628 GMT on Tuesday, 0.2 percent below Monday's New York close. Risk aversion has bolstered the dollar, seen as a safe haven, as investors remain cautious about the U.S. "fiscal cliff," which could push the world's largest economy back into recession. The euro is at a two-month low against the dollar due to concerns about Greece's own debt woes. ...