Flash player crashes. I am using Win 7 and flash 19

With Firefox, many of the hangs are related to the fact that we had to retrofit a modern security sandbox to Firefox.  Because that work isn't native to the browser, it's inherently not the best solution, but provides an important defense against modern malware.

Mozilla has betas of 64-bit Firefox for Windows available, which I believe include the native 64-bit sandbox for Flash Player at this point.  Moving to 64-bit Firefox may resolve a lot of this instability for you.  You can grab a beta of 64-bit Firefox here.  I'm really curious about whether or not this improves things for you.

Mozilla Firefox Web Browser — Download Firefox Beta in your language — Mozilla

If that doesn't work for you, I'd start at the video troubleshooting guide here:

https://helpx.adobe.com/flash-player/kb/video-playback-issues.html

If you're still stuck, please follow the directions in the guide on providing the dxdiag report and additional information about what you tested and saw.