I just setup a new PC with the new ASUS P8Z77-V PRO/THUNDERBOLT and am currently able to get one of my two thunderbolt displays working. The second one is outputting sound, but no video...
Are you daisy chaining your displays from that single Thunderbolt port? I don't think that will work.
Only Macs with dedicated graphics are known to be able to drive two thunderbolt displays on one cable. The on-board Intel graphics may not even be able to output that many pixels. (The spec says
You'd better connect your second monitor via another port.