hi!
I have indeed the same problem, altough I have a HP n54l but the same hdd as yours: seagate 3tb (st3000dm001). it freezes while it's copying, especially big files. while reading there's no problem at all. I'm pretty sure the hdd is the source of the problem because I have another hdd installed (wd green 500gb) and it doesn't face the same problem.
greetings,
sérgio.