I just searched religioustolerance.org and found nothing on Catholics banning interracial marriage. The accuser might be confused though, I did get a hit on Bob Jones Univ. and interracial marriage on the same page as the Pope asking for forgiveness for past problems. You can see the page here:
www.religioustolerance.or..._00mar.htm
As far as I know, the Catholic Church has never banned interraical marriage. If She did, you would have heard about it on the standard list of complaints on anti-Catholic boards all over the net.
It would be a silly idea for the universal Church to do so and certainly was not the case when the Spanish colonized the Americas.
Update: Here is another hit with Bob Jones, note that Catholic shows up on the page too:
www.religioustolerance.or..._choi2.htm
The search page:
search.freefind.com/find....g=en&fr=10
Gives this misleading description:
12. Charitable choice: Governments funding religious groups
about Roman Catholicism. Until recently, the university had forbidden interracial dating among their students. Edwards postulated the startup of a charitable choice program at a church
[url="http://www.religioustolerance.or..._choi2.htm"]www.religioustolerance.or..._choi2.htm [/url]
