There is a problem affecting (most or possibly all) Windows 7 users where a lengthy list of games will no longer start, because those games in question are trying to get updates from Games Explorer and Microsoft is now shutting down Games Explorer related servers. https://www.gog.com/forum/general/games_explorer_gameuxdll_and_rundll32_issues_with_offline_gaming/page1
For me the broken game is Darkstone. Other affected games include UT 2004, Sudden Strike, Blitzkrieg, Roboblitz, No One Lives Forever 2, Far Cry, and many others.
This batch file appears to fix the problem by disabling the relevant GameUX.dll files: http://ubeogesh-things.blogspot.com/2012/08/resolve-it-finally-game-explorer-aka.html
I have noticed that it also unfortunately prevents the original version of BioShock from launching if it is applied ("Failed to create the GameExplorer object"), and there may be other games that are also similarly affected. But the process is reversible by simply running the batch file again.
So, I think that first GOG thread should be pinned, for Windows 7 users that have problems with games not launching without an error message.