The answer is simpler than you think. Just look at the page you posted. It says many times on that page that the TV's native res is 1080i.
Ugh, I hate when TV manufacturers list it like that. Technically speaking, 1080
i can't be a native resolution.
You probably know this, but for the benefit of others: 1080i means an interlaced signal broadcast at 1920x1080.
Interlaced means it only sends half the lines on the screen at once, e.g. it sends a 1920x540 image with the odd lines on the screen then another with the even lines on the screen. This happen quickly enough that your eyes interpret it as a single image.
The overall image is still 1920x1080, which means you'd need a TV with that native resolution to display it without scaling. 1080p (the p stands for progressive) is the same resolution, it just sends the whole image in one shot instead of breaking it up into halves.
Anyway when manufacturers list 1080i as the native resolution it means the TV is 1920x1080 but for whatever reason doesn't support a 1080p signal even though, based on the number of pixels, it should be able to display that.
I don't think you'll be able to run at 1920x1080 as PCs essentially output a progressive signal. If you're PC is connected to the TV using a DVI-HDMI cable you can probably only use standard HD resolutions, in which case the highest res you can use is probably 1280x720.