Well, it's not Flash. It's HTML5.
Is your browser an older version?
Have you tried different web browsers?
When I load up the page, there's about a half second where the pictures have that circle going round, then they display.
If you're using a browser add-on that blocks scripting, like NoScript, you have to configure it to allow gog.com to run scripts or you'll see the circle going round instead of the pictures.
I don't know why you'd suddenly be getting the problem when you didn't have it before though -- unless your ISP is doing something it shouldn't.