I'm not using an old browser, but some naive spoofing. Which is apparently enough to run into IP blocks of this site, which happens to me regularly since a few days ago. I then have to press a button to get a new identity and everything is fine again.

After I figured out the privacy nightmare that user-agents are and that there's nothing you can do to any single user-agent to avoid this problem, I've opted to instead have the user-agent change every few minutes. Which includes IP information.