usb device not recognized on CentOS 5.2 over dell inspiron 531

I install CentOS 5.2 on my Dell Inspiron 531, everything is OK except that sometimes it will refuse to recognize the USB mass storage devide, and dmesg says that "usb device not address XX , error -100".

I finally resolve this by rmmod ehci_hcd, and then the device will be automaticly recognized and mounted.

I think this may be because that the ehci_hcd is stand in the way of the other proper handler of usb devide.