it seems there are serious problems with the coordination CyUSB.dll and LabVIEW / LabWindows CVI
There are several discussion at forum NI and at this forum.
I found only one way: Create a wrapper dll for labview in visual studio environment.
A good starting example for creating C # NET Class library for LabVIEW
My test version for CY7C65211 - USB-Serial Single-Channel (UART / I2C / SPI) Bridge:
and simple project for Visual Studio and LabVIEW here: http://mylab.wmsite.ru/moi-razrab/cy7c65211/
WRAP_DLL.zip 1.2 K