This weekend it's been taking a long time for click-throughs from campaigns. A link I clicked just now took about 30 seconds to go through to the site. The site itself is functioning fine.
Is this a known issue?
Actually, we learned that a large ISP in the US was under a DDoS attack and it was affecting connections all over the US. They've since announced that they have contained the attack so everything should be back to normal speed, but if you are still seeing a slow response, contact support.