@tedster - yes, I've investigated DNS hijacking & cache poisoning with my dedicated server provider. They assure me it is not happening. As far as pages not loading, that is doubtful. I run a dedicated server, not a shared account. It's on a very reliable top level hosting provider.
I've been investigating other problems and found one today that might be causing some problems. A while back I switched over to using Firefox exclusively. I rarely use IE. Well today I found that on my secure sign up form I had a tracking pixel that was "http". FF does not warn of secure / non-secure elements, but IE does.
So, when customers arrived at my signup form, they (the IE 7+ users, which account for the majority of my users)were seeing the secure / non secure item pop-up. That's a big no no and can stop a sale in it's tracks. If that is all this was, I'm gonna be kickin' my butt around the block for a few months. I don;t think it was the only reason, but it definitely impedes the sales funnel. I just adds the missing "s" and now no more warning.
Coincidentally or not, a few hours later and my sales suddenly opened up like gangbusters.
I guess this is just a reminder to check out these issues on a regular basis. Google's still not off the hook because this doesn't completely account for the yo-yo sales, but we'll see what happens.
Thanks for the info tedster. I'm hoping this simple fix resolves some of my ongoing issues.
BTW - as you know I have audio klaxxons on my key pages that I am very attuned to. In the past 30 minutes my site has suddenly come alive with what I'd consider "normal" to high levelsof activity. I still think these major algo update knock traffic down on certain sites for up several days.
Here to hoping for the best!