CANADA STOCKS-TSX slips as resources offset National Bank gain

* TSX down 31.21 points, or 0.20 percent, at 15,588 * Eight of 10 main index sectors decline * Talisman slips on news of struggle to sell itself * National Bank jumps 2.4 percent after results By John Tilak TORONTO, Aug 27 (Reuters) - Canada's main stock index eased on Wednesday after hitting a record high in the previous session as weakness in energy and materials shares weighed, offsetting a gain in National Bank of Canada after the lender reported strong quarterly results