I got flsh.hex on the root of my usb, I verified the md5 checksum, i tried both usb ports, and I even used minchkver.PUP. It actually says "SUCCESS... Wait a few minutes until console beeps and shuts down!" But my Ps3 instantly freezes afterwards and I have to switch it off and on again.
Btw Im using an 8GB usb formatted as fat32 with 32k clusters, and Im using redthetrainer's site instead of hosting my own server. Do you think that's an issue?
UPDATE: I used a different USB and it beeped three times and shut down without freezing. It may have worked...