Recently a LOT of people have been having issues with laggy gameplay, the Flash script stopping working and other Flash based issues.
There is one possible reason for this if you use Google Chrome, and that is that there are two versions of Flash "competing" on your system. This happened to me recently and caused the above issues.
Chrome updates Flash automatically BUT, if the Flash on your PC isn't up to date it can sometimes leave in a ghost second version that causes issues. Removing this means going into the bowels of Chrome but trust me, it's nowhere near as hard as you think.
First, click on the address bar above the window and type in - chrome://plugins (note the colon in the middle and TWO slashes).
Check the Details option top right, if it has a plus sign, click it.
Flash will likely be the first item and you will likely find you have 2 Versions and it will say:
Under that you'll see this:
Click "Disable" under the one that is located in the SysWOW folder.
Any plugins that are grey are disabled so your screen should now look like this:
Hopefully, if fingers were crossed and deities prayed to this may have helped your game along!