Time Warner says that GameTap parent Turner has decided to sell the subscription and ad-based PC gaming service. The parent media company's second quarter financial results released this morning showed an $18 million writeoff credited to the decision.  "There is considerable marketplace interest in the GameTap business and brand," said a Turner spokesperson of the pending sale. "We are considering various strategic options, but have reached no final agreement as yet. When there is a resolution, we will announce it."