You need to provide some more info: OS? IF Windows, do both show up in the USB devices? If linux, what's the output of lsusb? Does it show both devices or just one? Do you have them connected to a hub or direct?
For example, mine is connected to a laptop running Ubuntu:
# lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 12.04.3 LTS
Release: 12.04
Codename: precise
# lsusb
Bus 001 Device 002: ID 064e:d101 Suyin Corp. Acer CrystalEye Webcam
Bus 001 Device 004: ID 0403:6014 Future Technology Devices International, Ltd FT232H Single HS USB-UART/FIFO ICBus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 002 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 003 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 004 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 005 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Device 004 =
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Try bfgminer, imho it works better with asics.