The following C-code fails in ubuntu 10.10, but not in 10.04 This proves that It is a driver issue with the new kernel or less likely a libc issue. #define _GNU_SOURCE #include <fcntl.h> #include <stdio.h> int main (int argc, char **argv) { int fd; fd = open("/dev/ttyUSB0", O_RDWR); printf("fd has value %i\n", fd); }