hi!
i have bougth 5 mk4 navi computer from a germany seller..one for me and 4 for my friends...
3 of this work fine, but they are slow on startup...

the other 2 have worked for one minute after installation and than they died! i don't know why...the screen become black and the power led on navi is off..it work only if i keep the button pressed with finger..if i release it from mk4 the screen become black and navi died..i've tried to unplug connector and plug it again but the problem there is again..what can i do before ship these defect mk to the seller for change (thy are in warranty)..
any ideas?
please help me..i know i'm newbie but i need your help so much...