hmm... 5v to a 3.3v flash device... Sure way to destroy it and anything connected to it.
My experience in using the LPT for bad flashing...
If you can't detect the flash controller, YOUR SOLDERING IS BAD
Read errors - BAD SOLDERING
Write errors - BAD SOLDERING
Do I need to go on?
If you actually look around the internet for "Xbox 360 bad flash fix" you will find that you need to apply 3.3v to the NAND - NOT 5v USB!!!
But hey, keep busting consoles