Now, before I tell you this, please keep in mind that your situation may be totally different from mine.
About 2-3 months ago I used my ISP's "Control Panel" to re-direct 404's to my index.html page. (I had renamed a directory to lowercase and was trying to provide my users with something other than an ugly 404 page)
Well, the very next day I got spidered by AV, Google and one more I can't recall now.
Shortly thereafter (actually, the next Monday update), I went from #1 in AV for my main term, to #61.
In other words, I GOT WIPED!
Google rankings have stayed OK, but in AV I'm still subterranean.
But, like I said, your situation may be totally different from mine.