TV won't display 1080p, only 720p from laptop pc

[Dimfrop]

I've seen a few posts with similar problems, but no solutions have worked thus far.

I've got an MSI GX660r laptop with:
ATI MOBILITY RADEON HD5870
WIndows 8.1 Pro 64bit
All latest drivers for GPU and running latest version of CCC
Displays are connected via HDMI

and the TV I'm trying to connect to is a 40" Sony Bravia.

I have in the past managed to display 1080p on this display and I'm still able to with no problems on my Benq W700 projector and another little Samsung TV I've got, but for some reason, when I try to display (duplicated or solo) my laptop screen on this TV, it just comes up black. The TV will recognise that there is a HDMI plugged in and the pc knows that it is connected to a SONY TV.

I've exhausted everything I can think of, messing will all kinds of settings on CCC and uninstalling, reinstalling CCC and GPU drivers but to no avail. I'd appreciate some help/

Thank you,
James

 

[Dimfrop]

It's also probably worth mentioning that my Xbox 360 works absolutely fine with this TV even still.

 

[Omegaclawe]

Are you using HDMI or VGA? TV's rarely support 1080p over VGA, even if monitors can do it just fine.

 

[Dimfrop]

I'm using a 10m HDMI Cable, the same cable was used for testing with all the other devices (Xbox, Projector etc.)