My friend is insisting maybe there is a questionable link in the code somewhere and it's driving me crazy.
The images you presented don't seem to directly support that theory, but stranger things have happened. However, when checking your site for questionable links, none pop up.
This site sometimes helps in revealing odd things like that. http://www.unmaskparasites.com/ it didn't find anything suspicious at the moment.
...and, Google has not flagged your site;
Is there another message or error that Webroot displays that would indicate the issue with the link as your friend suggests? Or has someone experienced an unwanted re-direct or unusual pop-ups that don't belong on your site? What is it that is making your friend insist that there is a malicious link somewhere? - I'm not saying it isn't possible - just looking for the evidence, mind you. :-)
 I just downloaded thickbox.js and minified.css from your site.
I also looked inside of minified.css, and I see nothing that indicates anything unusual.