linux hang on transfer with rsync,can be a ram error?

My problem If I transfer file with rsync using tapes,or disk(usb,e-sata,firewire) linux hang,no way to resume if not using powerbutton(brutal shutdown!) sysrq-trigger don't work,ssh don't answer,keyboard and screen no input. I have a M5A97 R2.0 Asus board,with 16G ram Crucial. I 've ordered a couple of other ram by kingston In your opinion can be a hw problem,or ram problem? Using the program ramtest no error given. I have tried also this solution ..but hang anyway. Your opinion? I forgot,hang happen on every transfer especially with big files(over 10G) I tried different kernel versions..same problem.