HypersomniacLive: I'm not sure I followed everything you said, but I always clear everything in my browser history and my own games were identified and labelled correctly up until an hour or so into the Promo.
This is not related to browser history exactly. When you create a web page you can mark certain elements as cacheable. If they are present in the browser's cache (on disk, you usually need to delete it from settings), then the browser can display them right away. If not, the browser makes an additional request to get the required data. It's a trade off between loading a page quickly for the first time, or every other time.
The list of owned games is ideal for caching, because it need to be included in every GoG page, and because it does not change as much (it can remain the same for months). Right now, the system is probably overwhelmed by the amount of requests and status updates. And you won't notice the problem right away, unless you log in from a fresh browser.
