Below are some steps to follow if you want to resolve this:
Update: resolved the issue. Thanks for your input earlier, MN. This will affect all Kaspersky users in its default state, so I suggest TF2C's ad blocker detector, or the advertisers chosen (if they are the ones that determine ads can only be shown if targeting is enabled) be adjusted. Perhaps pass this on in a post somewhere?
Then something on your PC is blocking them; could be very much your virus scanner. The system detects if the ads are present or not; it doesn't matter what is causing it: adblock, anti-virus, ...
I'm afraid you need to figure out what's interfering with your browser...
Although Step 1 is reasonable, I should not have had to perform steps 2 and 3. Step two, as the name suggests, blocks suspicious activities, not ads per se. Step 3 doesn't block anything if correctly configured, it only detects, and yet it needs to be completely disabled, affecting all websites.
Temporary fix for Kaspersky users:
1.) Whitelist *tf2center.com* in Kaspersky's Anti-Banner plugin. I already had this done before the September ad update, but other people will need this too.
2.) Whitelist *tf2center.com* in Web Anti-Virus section of Kaspersky Settings.
3.) That still won't be enough. Disable Private Browsing completely in Kaspersky Settings. Kaspersky has the option to detect without blocking, and I know this works on other ad-required websites for me. However, this still triggers TF2C ad-block. Whether that's a result of detection at TF2C's end, or the advertisers' end, I don't know.
It is not necessary to uninstall Adblock Plus as long as it's disabled on tf2center.