If the power light is consistently flashing on the front of the unit, then it appears that the unit is in EM mode. Do you have the Nas Navigator software installed on your computer? If you do not, then this software can be downloaded here:
Windows:
http://www.buffalotech.com/support-and-downloads/download/nasnavi-256w.zip
Mac:
http://www.buffalotech.com/support-and-downloads/download/nasnavi-256.dmg.zip
After installing the Nas Navigator software, even if the unit is in EM mode, you should be able to see the device listed in the Nas Navigator. If you are able to see the unit listed here, then to troubleshoot, you would want to perform a forced firmware update, instructions available here:
http://forums.buffalotech.com/t5/Storage/FAQ-2-of-5-Force-Firmware-update-procedure/td-p/100317
Yes - from here, you would want to hardwire your unit directly to your computer using a standard Cat5 cable. After making sure that any wireless network connections have been disconnected, give the unit about 30 seconds before refreshing (or launching) the Nas Navigator software. Does the unit come up at a self-assigned 169.254.x.x IP address, or any other IP address for that matter?