I have a Forerunner 310XT that I bought about a month ago. It has worked well for me so far. However today I connected to my pc to upload my run data into Garmin Connect. I had two runs stored in the Forerunner. Only one run uploaded and one did not show up. I looked on my Garmin and no histories remain so it is gone. Has anyone had this issue? One other thing I have noticed is the battery does not last the 20 hours as advertised. I have been running quite a bit in temps in the 30's so maybe that is affecting the battery life.