Why doesn't Javascript work in Internet Explorer?

I'm trying to use Internet Explorer to test a website, but scripts don't seem to be running. This seems like it's an issue on a lot of pages - for example, I tried going to the Acid3 page, and it said I needed to enable scripting. I checked my security options, and Active Scripting is set to enabled in the Internet zone. I saw a suggestion on a website to try running regsvr32 jscript.dll; I tried that as well, and as a regular user, I got the following message:

The module "jscript.dll" was loaded but the call to DllRegisterServer failed with error code 0x80004005

When I ran that command as administrator, the registration succeeded. However, Javascript still doesn't work.

Any ideas?