Hi I too had this problem yesterday in fact. Although the tank was full, but having emptied it like yours the light stayed on. I took the back off expecting to see a sensor or something behind the tank, but there isn't one. I took the rubber hose off at the bottom where it connects to some sort of housing but only a dribble of water came out. However there is another black hose connected to this housing which runs forward underneath the drum. i took this off and again only a dribble of water came out. I then blew through this hose and could hear a lot of bubbling. I reconnected the hose, plugged the dryer back in and hey presto! its back to normal. It worked for me so must be worth a try! and should hold off a replacement for a while! Good luck!
By the way the hoses come on and off very easily.
Roger, September 2008