As of today, it's fixed. Here's the original post, though its contents are now outdated.
Somebody really, really hates PortableApps.com and has used Trend Micro against this site. Trying to access it from work prompts, not the usual work firewall (e.g. if I were to try to access, say, xbox.com), but one from Trend Micro.
The danger of accessing PortableApps.com is High, and the site is classified as a "Disease Vector", I believe it said. It did not make sense. I submitted a correction, saying the status should be Safe, and classified PortableApps.com as "Computers/Internet".
*sigh* They still haven't changed it. And I quote, "The latest tests indicate that this site contains malicious software or could defraud visitors." Also, the description of "Disease Vector" is as follows: "Sites that directly or indirectly facilitate the distribution of malicious software or source code".
Heh. Somebody really has an axe to grind. I guess they got a bunch of requests or something and didn't bother to check. Or... something.
Wanna help? Go here: http://global.sitesafety.trendmicro.com/
Type in "portableapps.com" and hit "Check now". See that their ratings are as I've said, or they've fixed it. I sent the corrections at around 4am Eastern time (GMT-5). So maybe they will fix it by the time somebody reads this. Also, Mr. Haller, if you see this, you can check "I own the site" or something like that on the feedback form. That should carry more weight.
Also, stuff like this is why I don't use firewalls like that, or Web of Trust for that matter. They can be co-opted for nefarious purposes and defeat their own purpose through social engineering. Don't trust them. Use common sense and trust what you can control.