The bug some of you were experiencing is related to the caching solution that we're currently testing and tweaking. Apparently for some users it was delivering a wrong (old) html of a publicly available page
(one that's the same for everyone). In the worst case it meant that you might see a random avatar and a wrong cart on top, but there are no user details there and you cannot make any changes to it either as it's a cached thing (think read only).
More importantly, all your personal data and content (your games, PM's, order details) is safe here, as it is always delivered over a secure connection and is also NOT cached, therefore nobody can see your games or messages because of the bug outlined above.
Last but not least, for the time being, the caching solution will be taken down, until we can nail the issue.
Most importantly, I think I speak for us all to say - Thanks for getting out of bed to deal with this (not that I know that you were 'in bed'). It was the right course of action for GOG to take, and we appreciate it.