[2014-01-14 03:01:36] setrlimit: Changed soft fd limit from 256 to 1024 (FD_SETSIZE=1024; hard limit=unlimited)
[2014-01-14 03:01:36] Started bfgminer 3.9.0
You either do not have the Silicon Labs driver properly installed or the device is not recognized. You should see output regarding /dev/cu.* devices and you should be able to see /dev/cu.* devices with the AntMiner U1 plugged in:
ls /dev/cu.*
https://discussions.apple.com/message/10895748#10895748