Please show a screenshot including your entire Composition panel.
Make sure that there are no effects applied to your paths in Illustrator. Many effects cause AE to rasterize the path.
If that doesn't clean things up check the interpretation of the footage. At the bottom of the panel you'll see a button called More Options. Click that and set anti aliasing from Faster to More Accurate.
If that still does not work try turning off Open GL. If your footage .ai layers don't look great at 100% scale then you may have Open GL issues. They crop up with the art is way too small. Generally your file should be at least as big as your comp. IOW, SD .ai artwork should have an artboard or document size close to 700 points / or pixels by 400 points / pixels.
I hope this helps.
Are they actualy vectors? You know, one can embed pixel graphics in AI as well plus AI uses bitmap effects for drop shadows and that... Just because it is an AI file doesn't mean nit has infinite resolution...
Any chance you've got pixel aspect ratio correction turned on for your comp?
If so, try rendering out a quick test segment. The issue may not be there.
Szalam's suggestion is one of the several that made me ask for a screenshot of the Composition panel.
Also, I just want to check to see whether the pixelation is happening during scaling (which it shoudn't) or during a zoom in the Composition panel (which is normal).
Fixed! Rick and Todd, both of your suggestions helped.
Todd, I realized that in some instances I was zooming and not scaling. Making sure I always scaled improved the quality quite a bit. But even when I scaled the graphics, they still didn't have the same quality that I have gotten in the past with previous vectors. So I then selected interpret footage and set the antialiasing for my eps options to "more accurate," as Rick suggested.
I've now got the quality I know the images should have.
Such a relief. Thanks for all your help, everyone!