freeze up?

i have a sansa clip that i hooked up to my mp3 wireless modulator. it is one of the ones that plugs into the cigarette lighter and has the display on the front and a remote. the ear jack worked but had to change by mp3 player and sound was not that great. used usb cord and i could use the romote and it read on the face of the modulator and sounded great then it froze. any ideas?

Slide the power switch up and hold it there for 15 seconds. That forces the Clip to power off.

why is it doing this though?