When i start up Skyrim from steam, I can get up the the main menu, and load my save, but while its loading, the screen goes back to the desktop and last time it said there was a 'rendering' problem...how can i fix this?

You didn't mention machinery, OS, video card, etc, so we'll wing it.

Could be a couple things to ponder. Has the game folder become corrupted somehow, or has something changed with the video card?--"rendering" would tend to make one think so.

Has there been any changes to your video driver(s). You mention loading a Save, so it's apparent it work ok before. "Rendering" would seem to indicate a video card/driver/DX issue...it's possible a driver got corrupted. First thing, would be to go to the card mfr directly to get the latest CERTIFIED drivers. If installing those doesn't work, try swapping the card with a known good one, and go from there.

(* You may have something like an Asus card with an nVidia chip--I prefer the latest drivers from nVidia, but that's just me).

There really are a lot of little things to check out, but these are the basic ones to tackle first...never hurts to have the lastest video drivers, or DX.
How old is the card? Those with fans can act funky when they overheat--if it has a fan, make sure it's turning. I'm running through Steam also, and no issues.

Others here may have more options to look into, so see how it goes...may be "none of the above" for all we know.

I think im onna try re-installing, since it appears to be an issue with the installed game,