Does the Asus provide gps sharing through a virtual port scheme. If so this may be your problem. The workaround would be to implement your own polling and NMEA sentence data parsing routine. I experienced a problem on an HP Travel Companion with the serial port data received events when the virtual port feature was being used. The virtual port feature is intended for sharing of the gps port by multiple applications. When I disabled the feature and accessed the port directly the data received event was fired. If I enabled the feature I had to use a polling routine to get the serial port data. I do not think that this is a bug. I am not sure how I would implement a data received event for multiple listeners when using virtual ports.