problem in recognizing sandisk usb flash drive

Hi We have developed an embedded product which reads files from the usb for a specific application. We are using lpc2478 controller and using the usbhostlite stack recommended by phillips semiconductors.We are able to detect all pendrives except sandisk make. We suspect something problem with power requirements. Could anyone tell the details of the power requirements of sandisk usb flash drive in all modes of operation? Thanks and regards.