maybe this solution will help some other guys, facts first:
win7 64bit w all updates
matlab 2015a 64bit
picoscope 3203d w/o mso
picoscope software v188.8.131.52
picoscope driver v184.108.40.206 (07.04.2015)
asrock mainboard 980de3/u3s3 r2.0 w etron usb3.0 controller driver v0.118
i couldnt get my picoscope to work on my pc on usb3.0. on usb2.0 there are no problems in my matlab code or in picoscope software. with the etron driver version 0.115, and the upon described constellation, i get it to work.