I'm not sure this is the same problem as the Inconsistent consecutive days bug that is reported, but maybe more like the problem this user had. I'd post under that topic, but it appears to have been resolved as "By Design".
I've been monitoring my consecutive days recently and yesterday had a total of 12 consecutive days, yet today when I first look I had one, but now I have two consecutive days. Am I missing something? I work in GMT, so there is little chance of "missing the Stack Overflow day". I don't necessarily answer a lot of questions, but I have recently been visiting my profile page to check badges / rep / consecutive days, and the homepage (and unanswered questions) for questions I can answer.
My guess is that it thinks that I missed Sunday (as that was the day 2 days ago ;) ). I'm pretty sure I at least visited the SO homepage in that time and maybe additional pages (though, that I can't be sure of).
Is there something more than just visiting stack overflow that you need to do to acquire a visit? View two pages / the homepage is excluded?