I have an ep121, and I have been experiencing the pen going unresponsive as well as touch. When my pen goes unresponsive the system says unknown device and I hear a whine coming from the bottom of the device. I called Asus today to try and get my slate replaced. I have sent it in once before for pen calibration issues and it came back with no change and it took about 30 days. I have been following the RMA thread and have seen other people get their slate replaced for the pen and touch issues. When I called asus I spoke with a Representative who was very nice and assigned me a case number, however his manager was unavailable so he sent me to the managers voicemail where I left a message. I shall give them 6 hours then I will call to follow up.