Computer Specs:
Operating System: Windows 7 Home Premium (Service Pack 1)
Processor Type and Speed: Intel (R) Core (TM) i7 CPU 860 @ 2.80GHz
Amount of RAM: 8.00 GB
Graphics Card: ATI Radeon HD 5570

I'm having an issue with my Sims 3 game that makes random objects in the game stretch across the screen. Along with this, sims clothing and ground textures are blurry, making images nearly impossible to make out. When this problem occurred, I hadn't played the sims 3 in about a year (no specific reason why, I had just gotten bored with the game) and booted it up again around 2 weeks ago. I had played on another user on the computer that has never had custom content or mods and decided to play again but on my user with all my mods and cc.

The main issue is the stretching of graphics and items in the game. First, I booted up my game and opened an old save. When I opened this save, there was a very large swipe-like stretch across the screen and to the sky (in map mode), which seemed to be rooted at a staircase. The staircase was invisible, but sims could still walk up and down it. I tried quitting the game and creating a new sims in a new world. There was still the same issue even on a clean slate. This problem happens every time I open an old save and make a new one, making it impossible to play the game with this stretch blocking the screen.

To fix this, I referred to the FAQ and first tried to delete cache files, booting up the game checking it was fixed, then tried deleting launcher files and booting up the game. I did this with Thumbnails and WorldCache files and found no solution, nothing had changed. Next, I removed all my custom content, first removing package files and booting up my game. Finding no result I then removed the Sims3Pack formatted content. I also checked AppData folders for the user I am currently using and could not find Electronic Arts in Program Files (x86) so I deleted my cache files again and booted up the game. This led to the same issues, maybe even a more drastic stretching than before. Lastly, I renamed the user file "The Sims 3" in the Electronic Arts folder to "The Sims 3 Backup" then booted up my game. The results were horrible, I was left with even more stretching and a grey screen with lines all across.

I do not know what more to do. I figured it was an outdated custom content issue, but after removing it all, there was no fix. I have never encountered anything like this and it is quite odd it happened now rather than before.

Wow... I've never seen anything like that before, but a quick google search revealed this page, and mentions that ATI Radeon graphics cards need 'Adaptive Anti-aliasing' enabled. The link they reference seems to be dead but you might be able to find more info by searching the EA website. Also maybe try updating your graphics drivers?

edit: I couldn't find anything on EA's page that's more in depth, but I think these are the steps.

The link that you gave was very useful. I was able to fix the problem by using the "Restore to Factory Defaults" in my graphics card settings.

Thank you for your help!

My pleasure, glad it worked!