Alphasmart NEO 2 delete typed letters automatically

I just bought this device for typing my learning material, it works perfectly firstly, but something wrong happened later, the NEO 2 will delete letters automatically, like an invisible finger pressed "backspace" on keyboard.
It's definitely weird, I doubt whether there's dirty, grease or water under the keyboard, I check it, it's OK. Did it result from software error? So I restore to the factory defaults, but unfortunately the problem is still there?
Could anyone help it, many thanks!

[thewonderfulwizardofozisan]

Definetly looks like the backspace thinks it's pressed down. Try to press the backspace button severel times, holding it down and letting it go. See if you can make it not delete text for even a few seconds. It's not a software fault, it's either the key or in the connection between the keyboard and the mainboard. Try cleaning under the key, try disconnect the wires and connect them again. Good luck!

[muskndusk]

I see by the date that you put this up some time ago. Ask at the Flickr Alphasmart group. This is really weird. Are you sure there was no pressure on Backspace?