As already suggested, please try a different brand of USB stick.
Also, many BIOS's support various USB boot emulations, i.e. "USB boot as ---> HDD, Zip drive, CDROM" etc.
I cannot recall them off-hand, but I have such a BIOS somewhere so I'll take a refresher on it later
Anyway, go and look through your BIOS and see if it has any of these USB boot emulations and try them.
Finally, can we clarify..........is this BT3beta or BT3final??