This indeed seems a hardware problem. However it only happens when power drawing devices are attached (like my external HDD or the displaylink screen). USB drives works without a hitch.
Well it wasnt my laptop but the Fresco Hostcontroller driver! I downgraded to V3.4.6.0 as suggested in
http://forum.notebookreview.com/asus...sus-g53sx.html and it works! It also fixed the frame stuttering problem, it finally keeps running fluid! Thanks for your help!