That's what we call the "slow script" dialog.  Flash Player is a language runtime, a lot like Java or JavaScript.  We run software written by other people.  When we observe that content is using an excessive number of CPU cycles, such that it might lock up the machine or browser, then we interrupt the script and give you a chance to terminate it, so that your system does not become unresponsive.

In this instance, Zynga writes really complex content.  In fact, some of the most complex content we know about.  They're also directly across the street from our office, so we're easy to talk to.

Zynga is in the best position to troubleshoot their application, and in the unlikely event that they need our help to identify and resolve the performance problem, they have easy access to us.

In terms of things that you can do, reboot the computer (seriously).  If the problem persists, close all of your other open applications and browser tabs, which compete for system resources.  

We run on a couple billion systems of varying age and capability.  To get the best possible experience for the system at hand, we make a fairly direct trade-off between CPU usage and available system memory (the more memory, the more we can cache things to reduce re-processing graphics and such -- the less memory, the less we cache, and the harder we lean on the CPU).

Memory gets fragmented over time, and applications not only need free memory, but they need free contiguous memory.  Rebooting the machine periodically is a healthy activity, and will solve any active memory fragmentation situation.  Running a minimal amount of other stuff while you're playing the game will ensure that you're not encountering CPU pressure from other applications or open tabs running simultaneously.

Moved to "Using Flash Player" forum.