got it in the mail today, turned on fine, but as soon as i hit a pad it starts shutting off and on and blinking 303 on the LCD. I can't push any pads or adjust any knobs until I turn it off/on again, but it keeps happening. Sometimes I can play a pad, adjust the bpm but it'll eventually shut off. I haven't gotten a memory card for it (i'll probably get a 64 mb), but not having a memory card wouldn't be the cause of this, right? I'm confused.

sounds like the infamous fcked 303 power supply

I think theres some posts regarding this in the 303 section (tips and tricks)

try a different power supply (search for a boss brand) and limit the amount of on/off switching.

honestly I would send it back if you can. good luck