Try reinstalling the driver with zadig.  When I first plugged the U3 in, Windows installed some weird driver that doesn't work.

Then, play around with the voltage and frequency settings until you find one that sticks.   Unlike fullzero's list of results he posted, most of those combinations resulted for me in it not finding the device at all.  It also never find the device right away, it takes a few minutes.

I'd also try and just have one hooked up and see if you can get one working first, then try the other.

My results on Win7 64 bit, using fullzero's suggested settings, were hashing at 30 GH/s for 24 hours with no issues other than it's only half the advertised hash rate.  Then I switched to the Engineer's suggested settings and it was hashing at 40 GH/s for about 12 hours when it quit hashing for some reason in the middle of the night (no error codes on cgminer, just wasn't doing anything more than hashing at a negligible megahash rate less than the old school block eruptors), so I restarted the PC and it's now back running at 40 GH/s.  So I'd only consider my results partially successful, so far.

Tried the new instructions, with the Engineer specified frequency and now I'm hashing at 40 GH/s.  I was hashing at 30 GH/s on some other frequency & voltage settings before. 

I'm pretty disappointed in this device so far.  This would be my seventh bitcoin machine I've set up, including AntminerS1 and AntminerS3 and this is by far the most hassle and most amount of time wasted simply trying to get it to work at all.