Yes, active text won't work on URLs. We had a few issues where active text was translating portions of URLs that it shouldn't have and breaking links.
You could possibly use the MySQL replace function to do a query that would actually change these in the database itself, but since they're probably a full url, it might be a bit rough to form the actual query needed.
You can try posting a post or two that contains the link, probably need to view source so we can see the entire html. Feel free to change the actual site names if necessary.
