It's permanently frozen

I got this zen vision m since 7-8 months ago and sometimes it freezes, but when this happens, i only have to reset it and everything works fine. But yesterday I was watching a video and it froze... but when i reset it, it was still frozen, i mean the letters appeared( u know: Zen)but nothing else happens, it doesn't rebuild...
So i waited 'til the battery runs out; i charged it, i turned it on, and was still frozen!!! i reset it and ...nothing....still frozen.....

Any suggestion>?