Ubuntu 8.10, series dv6000, usb serial port

[willydlw]

Running kubuntu 8.10 on my hp laptop dv6871us. Am able to connect to Windows hyperterminal with a Prolific 2303 usb to serial adapter and null modem cable. Have a c++ program that needs to open, read and write through a serial port. This code running perfectly on a friends Compaq laptop with gentoo. On my hp laptop with kubuntu 8.10, a friends Compaq laptop with xubuntu and a Del desktop with kubuntu 8.04, the program code gives a valid file descriptor when opening the serial port but fails everytime on the read call, always returning -1 with error Temporarily unavailable. We know it's not a code or cable issue. All users are members of the groups tty and dialout and have rw permission to ttyUSB0 and ttyS0. What are we missing in our ubuntu installs to be able to implement serial port communications?