Streaming Issues on New LG LED TV

Hi guys, im not sure what category this fits into but i'll try and make as much sense as possible.

Long story short - we had an old Palsonic 42inch LCD TV that broke about 2 months ago, now we used to watch movies from the pc through cat5e cable to my PS3 and then that was hooked via HDMI to the TV, never ever did we have any issues.
Until we got a new TV via warranty which is a LG 42inch 3D Smart TV, the TV works great but when we stream movies again we now have huge buffering issues and the movies constantly stopping, its very very frustrating.

to try and solve the issue ive upgraded my Cat5e to Cat6 - i move the movies from my external hard drive to my primary and try stream through there both of which are not doing anything. I'm in the process of preparing my PC for a format because it is running slow and it could use with one.
I guess im wondering if anyone has had this issue or heard something similar? im wondering if my 1TB externan hard drive which has 150GB space left on it is actually suffering and thats causing issues? or the fact that my old TV was 60HZ and the new one is 100HZ? or if my transcoding settings on PS3 media server need changing? or if its a mixture of them all together?
Seems strange though that as soon as i plugged the new tv in there has been issues.

Thankyou in advance to anyone who replies.