
i had this problem, and it's been serviced (replaced power supply).
but here's an interesting work around.
Some C300 units shipped with the wrong power supply. The Tablet PC may drop keys or the mouse randomly moving to the lower right. If you look on the side of your power supply and see adt#APT3503001XXXXXXXXXX then contact Acer Support for a replacement.
An interim fix is to lower the brightness of your C300 2-3 settings while on AC power.