A funny thing is happening on the way to the ballyhooed ad slowdown: The big media companies keep posting record ad revenues.Boosted in part by its huge hit Survivor on CBS, Viacom ( VIA), the world's third-biggest media company, Tuesday posted a 22% jump in cash flow. The company pushed past analysts' estimates by 4 cents amid strong ad sales at CBS, MTV and its radio stations. Viacom, which completed its deal to acquire CBS earlier this year, said profits fell 65% on higher expenses from that deal. Net income fell to $33.4 million, or 2 cents a share, from $96.7 million, or 16 cents a share, a year ago. Pro forma cash flow, a key financial measure for media companies, rose to $1.45 billion from $1.18 billion, also well ahead of analysts' projections. Pro forma revenue rose 7% to $5.97 billion from $5.58 billion. Analysts surveyed by First Call/Thomson Financial projected a loss of 2 cents per share.