We have a TestStand/LabView application that creates a serial port error that locks up the serial port and often Windows XP. The only way to clear the error is to reboot the PC. The application is being run on a Dell Precision 670(3 Ghz Xeon), 1mb RAM & communicates to multiple RS232/RS422 serial devices(10) at 57600. The multi-device commuciation is handled by SIIG CyberSerial 950 high speed serial cards(128 byte FIFO) & the FIFO's set at 16 bytes. Any ideas why our app crashes the serial port & XP?