By DAN STRUMPFNEW YORK (AP) ¿ Winnebago Industries Inc. posted its third consecutive quarterly loss on Thursday as sales of RVs continued their downward slide amid locked-up credit markets that make it difficult for consumers to get financing. "It's extremely challenging to compete profitably in a market of this nature," Winnebago Chief Executive Bob Olson said in a conference call. The recreation-vehicle maker said it lost $10.4 million, or 36 cents per share, in its fiscal second quarter, which ended Feb. 28. That's after a profit of $2.5 million, or 9 cents per share, in the same quarter last year. Wall Street analysts were expecting a narrower loss of 31 cents per share in the most recent quarter, according to a survey by Thomson Reuters. Revenue plunged 81 percent to $31.8 million from $164.2 million, falling short of analysts' estimates of $42.7 million in revenue. RV dealers have been closing their doors across the country as consumer spending falls. Increased incentives have largely failed to lure buyers. Sales of RVs are closely tied to discretionary spending, which has fallen sharply in the economic recession.