Bootloader usb mode when connect it to computer

Bootloader usb mode when connect it to computer, i hear sound that pc recognize something but dont see it in devaces and discs

yesterday sansa works perfect;

now i see

panic

mount 0

pc 308011bc sp 301005l

bt end

now i have connected sandisc battery charge but dont see player in pc

It may be a problem with the cord. There are two separate connections, data and power. If the cord is fraying inside you could get a power connection without a data connection. 

See if you can borrow or buy another USB to mini-USB sync cord.