Note that the original poster, JS_Harris, identified the source of the problem soon after posting, so he didn't need feedback on his questions. His post, though, which has been sitting in our Google forum premod area while I've checked things out, rang some bells about other discussions we've had in WebmasterWorld about spurious traffic... and I've felt this post should be published, but with the condition from administrators here that (at least for now) we not identify the site or sites causing the problem.
Let's say simply that in this case, the source of the problem turned out to be a generic browser testing site, one which is intended to be benign and which used browsers on distributed computers to capture some data from their respective locations. I hope that doesn't mischaracterize what the setup is.
A thread that this post brought to mind for me is this one that's been running in Analytics from Feb 21, 2012 until now....
Logs Show Surge, but Not Human?
I doubt very much that this is the same thing as the surge thread. There appear to be many non-parallel aspects to that discussion and this one. At the same time, there appear to be some similarities, and it struck me that this might be of general enough interest to post here and prompt further discussion on the overall topic.