I've got the a similar problem. After 1 or 2 hours, the device either registers no keys at all or multiple strokes (20+).
Last time I checked, my syslog shows multiple entries "usb 2-5 reset low speed usb device nr 5 using ohci_hcd" after the device stopped working.
If the device registers to many strokes, it can be interrupted by pressing a key on the real hardware keyboard.