Well, I ran scans using the latest definitions from several programs and found nothing that accounts for this. I confirmed that it only happens with vBulletin, as other areas of the site and external sites do not call the address I mentioned. I disabled the ads and all other custom vBulletin code and the site is still accessed, at least for me, whenever any vBulletin page loads. Does anyone else have this issue and/or know how to fix it?