DLPC350: DLPC350 USB connection ISSUE

Part Number: DLPC350
Other Parts Discussed in Thread: DLPLCR4500EVM

Dear Engineers:
  I encountered some issues while connecting to a PC using DLPC350, please kindly provide assistance.
1、I made a DLP control board using DLPC350. The basic design is based on Ti's DLPLCR4500EVM
Lightcrafter schematic.  
2、Power supply for DLPC350 is OK.
I connect the USB to PC,but the LightCrafter4500 softeare v4.4.1 shows not connected. The PC device manager shows a new USB device,but Unknown USB Device (Device Descriptor Request Failed) 
If there is any help, please let me know.Thanks