RIM (NYSE: RIM) shares have enjoyed an unlikely rebound this year. Following the release of third quarter results, investors were surprised by the positive results and strong cash flow positions, which sent the stock price up. Now, an upgrade from Goldman Sachs (NYSE: GS) are pushing the price even higher. RIM advanced 4 percent to $11.54 in New York yesterday. The Waterloo, Ontario-based company’s shares have gained 46 percent since the end of October and advanced on 10 of the last 11 trading...