Take a look at these:
- http://forum.ea.com/eaforum/posts/list/7649402.page
- http://answers.ea.com/t5/The-Sims-3/Origins-Installation-Issues-Sims-3/td-p/1401496
First link has a variety of stuff suggested - including creating new folders, etc - just read through the posts.
Second link is to try running Origin as admin
- To do so, close Origin and right-click on the Origin icon and choose Run as Administrator
I would recommend trying the second link - running as admin - before the other one.
