Help Antminer u3

[nandopais]

Good morning, please someone help me. I have two antminer u3 installed on my windows computer running on cgminer 10. 4.9.2.
my problem and that in less than five minutes appears to me that cgminer error.

when using a single miner everything is perfect, but when I add the second me of this problem.

au3 1 attempted reser got err:(0) libusb_sucess
au3 1 getresults usb read err:9-9) libusb_error_pipe


I do not know if this right but I'm using a * .bat

Start batch:
cgminer.exe -o stratum+tcp://stratum.antpool.com:3333 -u nandopais.1 --au3-freq 237.5 --au3-volt 750 --api-listen

please help me...
 Thank you very much for your attention