As this is a site rating issue it's been moved into the main SiteAdvisor section (Home and Home Office / Web and Email Protection / SiteAdvisor)
I ran a number of checks on the site. It comes up as either clean or not yet rated in most of them. Sucuri notes that SiteAdvisor has blacklisted it.
SiteAdvisor itself gave the site a Green rating, and when I brought up the site the SiteAdvisor icon was still Green. However the site page displays a Red warning which comes from TrustedSource, indicating a recent problem. The TrustedSource page for the site indicates a problem which started about April 8th but doesn't say what it is. The problem cleared, then came back.
IP address checks show this is a secure GoDaddy server based in Scottsdale Arizona. It is not currently showing on any blacklists, but Project Honeypot has a report showing it was blacklisted about 8 months ago for sending spam. The server will be hosting many websites so it's not possible to say which site was responsible. It's not blacklisted now, so the problem is most likely on this website only (although don't overlook the possibility that this is backwash from another site's bad behaviour).
I can't test the site fully without installing Java, since the site requires it. I also have multiple site filters on my everyday browsers to block advertisements, cookies, web beacons, and other trackers, and the builtin security settings are pretty much at max. To do testing properly I need a basic browser with Java and no add-ons, and I haven't run any tests yet in that environment.
I would advise at this stage you follow alexn's advice. This may be a false positive, but if it's not the SA team are better placed to tell you what the problem is than I am.