Can a BOTW Listing Cause Major Google Juggle?

Hi all,

I've got 2 websites that are both pretty much the same size and design, and both in the same niche but with 100% unique content on each.

They've been doing well traffic-wise, and they've been making me good money. Last week I took advantage of the Best of the Web birthday sale, and ate the $600 to get both sites listed.

Sites were accepted immediately and crawled on BOTW right away. The very next day my traffic on each of these sites took a dramatic drop, and for the past 4 days the traffic is literally 1/10th of what it was before. Keep in mind that these sites are over a year old.

I've built NO other links to these sites for several months now, with the exception of maybe a half-dozen Yahoo Answers links to each.

So my question of course is this: did the BOTW listing cause some kind of google sandbox affect? Could this one new link be so powerful that it sandboxed my websites, even temporarily, to such a huge degree?

I understand a website will jump in rankings from time to time, especially if you build a lot of links at once, and I'm also pretty sure these sites will return to page 1 for many of my search terms. But this is something very weird, something I've never seen before, and I guess I'm putting this out there as a word of warning (because if I could go back I'd probably not have listed the sites at all, or at least done them one at a time).

Anyone else see this type of thing happen to them? Or can anyone offer some type of alternative explanation?