I am experiencing the same exact thing. Have Lilliput 7" 619GL-70NP/C/T. The touch functionality works great for anywhere from 30 seconds to several hours before it locks up for no reason. Unplugging the usb connector and reconnecting it fixes the problem as does restarting the pc. I am trying to determine if the monitor is defective or if I have some interference. I don't think it is a driver issue since I used two different versions on two different computers with the same result. Please let me know if anyone has found a resolution to this.