I had the same issue in July. After replacing the gas cap with OEM part, and 5-6 warm up/cool down cycles over the course of 4 days, the lights went out and have not returned.
Went ahead and replaced the sensor that was suspect, per the OBD code. Surprise, surprise. seems to be doing the trick. Thanks [MENTION=66389]BlackWorksInc[/MENTION] for the moral support to give it a go. BTW, Bank 2 Sensor 1 was much more a PITA than I imagined to get to. Fun times.....