Thanks for the replies; I did verify that there was air in the tank. I tried again this morning, and still no dice. I guess I'll have to take it to my LDS and see if they can help. I might try rebooting my computer. On a different note, this incident made me aware of a few other issues. Three lessons that I learned in OW class were brought home: Plan your dive then dive your plan, don't give in to peer pressure, and have a damn backup. I'm really new to diving (29 dives now) and this was the first time I had to cancel a dive because of an equipment issue. My dive buddy is an experienced diver that hasn't been in the water for a while. We have dived together a few times now, and use air at almost the same rate. He suggested we dive and turn when he got to one third (rule of thirds). Of course I had to decline. Lastly, I bought me gear used from a friend, and was impressed with a two hose set up (second stage and LPI hoses). I have the transmitter and use an Air2 for an alternate second stage. I really thought this set up was great; I'll now use an analog SPG in addition to to AI (if I ever get it working again).