Flash Player videos stop playing when you change the video's resolution to full-screen mode.
This is a known issue on some computers with Intel HD Graphics when runing Internet Explorer 9.
Try one of these solutions first:
Reenable hardware acceleration after this problem has been resolved to enjoy the performance benefits of hardware acceleration. If you want to reenable hardware acceleration, follow the steps listed above and deselect the Use software rendering instead of GPU rendering check box.
On some systems, you can resolve this issue by updating the Intel HD Graphics drivers. It has been reported that driver versions 188.8.131.521 and above do not exhibit this bug. Unfortunately, some systems require updates directly from your system manufacturer. Adobe is working with system manufacturers to make sure that they include the latest drivers in future releases.
Systems with Intel HD Graphics adapters running Internet Explorer 9 have this issue.
Hardware acceleration is a new functionality of Internet Explorer 9. It allows Internet Explorer to move all graphics and text rendering from the Central Processing Unit (CPU) to the Graphics Processing Unit (GPU).
Flash Player 10 and later can use your system’s graphics hardware to accelerate video decoding, and can also accelerate video presentation on some sites. Starting with Flash Player 10.2, Flash Player also takes advantage of hardware accelerated graphics in Internet Explorer 9, using hardware rendering to improve graphics performance.