I have a 4 month old i550. I have 18 dives with it. Noticed after last dive (3 weeks ago) that it seemed to take a long time to turn off but I didn't pay much attention to it until I went to test my gear yesterday before leaving on a two week dive trip (in a week) and found the unit dead. The battery was shot so I bought a new battery and installed it. Booted just fine but then it went into this Surface Interval / reboot cycle described earlier. It counts a surface interval up to two hours and then reboots. I have hooked the unit to a tank of air and it responds properly to tank pressure. I have downloaded dives to DiverLog with no problems. But today I noticed that the clock had run 2 hours slow over the past 20 hours. I need some advice from someone with experience and / or knowledge. Is the unit safe to use for diving? We are doing a two tank dive one morning, then off the next day, then another two tank dive, then off for two days, then repeat so I really don't care too much about the "safe to fly" because we will be done diving two days before flights. I am mainly concerned about general functionality while diving. Thoughts? I cannot believe there isn't a master reset capability with this device. You would think that if you took the battery out for 24 or 48 hours it would reset itself. Thanks