Lowe's results miss, says it sees uncertain demand

* Shares up 1.1 percent (Adds Q3 outlook, background, stock activity) NEW YORK (Reuters) - Lowe's Cos missed quarterly profit and sales estimates as benefits from the homebuyer tax credit and cash for appliances programs waned, and the retailer warned of uncertain demand. The second-largest home improvement chain after Home Depot also forecast current-quarter profit of 28 cents to 32 cents a share, while analysts were expecting 31 cents. Sales at Lowe's and Home Depot had benefited immensely in the first quarter, which ended in April. Many