killing music player

I have done the same thing to five different phones, out of the box the
music player works ok, I load a few hundred tracks, it will then go through
a long proceedure of updating music library, starting music player and might
eventually play a track, if I try to play another the phones reboot and does
the same thing again,I have done a factory reset and tried a small memory
card or none at all, It appears I have somehow permantly crippled the
player,

So frustrated with this I started to search the web, I have come across KD
player, a free java app that works ok once you have figured it out, but it
is still annoying as to what has happened with the original player, the
phones in question are four 6300's and a 5200, all brand new some branded
some brand free, seven different memory cards