The challenge system is dependent on CloudFlare. Sometimes it takes a few seconds. Sometimes it takes get-a-cup-of-coffee time. That's not under your control.
For some reason, it has decided my IP is a threat and I have to be checked out every time. It's honestly a mystery as to why...it shouldn't be happening...and eventually it should work out I'm not a problem, but that doesn't seem to be happening. It's lasted through a rooter reboot. Maybe it doesn't like Verizon? I do not normally have this problem with CloudFlare... In fact, I have never had this problem with CloudFlare before. The very occasional check now and again, but not 100% of the time on a specific site like this.
And I also do VERY occasionally get rate limited just clicking through to the discussion forum, like Atramentous mentioned.