hi, it happened to me once too... the reason is certainly the kernel which is not compatible with the soft that you sent previously,
1* you have to keep your thumb on the Red LED... and turn on the power ...you will have to do this several times until it works...a friend of mine confirmed that he was able to revive with my backup but he only sent the file...(rootfs.tar.bz2)...any will do doft with that file,
2* you just have to press your thumb on the red LED and turn on the power, if not there is only another way (mini usb) as is done with 800se...but you have to download the driver for the mini usb.