The games freezes if you do the following on Mozilla Firefox:
-open new tab
-go to another tab
-open the desktop
-minimize Mozilla Firefox
-use taskbar
-similar things/etc.

the solution:

Instead of a "false" marker at plugin interactions, the marker is now automatically set on true. You have to Change this by hand and save it:
1. Open: about:config in your browser adressline
2. Accept the security risk message
3. Search for the following (it is sorted alphabetical):
dom.ipc.plugins.asyncdrawing.enabled
4. The norm in this Task must be set to "false". With the update this might be set on true, so you have to Change this.

worked for me... have fun