Re:. Flash applications freeze periodically with sound but no video on all browsers.

I've been having problems with flash applications on browsers for the past year or two. What happens is that when a flash video starts, my browser will lag periodically. The sound will be present, but the video will freeze, and I will not be able to switch tabs, click on buttons etc. This was most noticable on YouTube at first, but it's also occuring with other sites, and it's very annoying when a site has flash ads and it causes my entire browsing experience to slow to a crawl. This isn't just a firefox problem, I've tried IE and google chrome as well, and I have also tried different Internet connections. I've tried various suggestions to fix it, such as turning off hardware acceleration, uninstalling then reinstalling flash and shockwave, reinstalling my video codecs, but they all have no effect. Can anyone help me with this problem, its driving me nuts! My browsers are all updated to the latest version, my flash player is version 11.7.700.169, and I am using Windows 7 pro (6.1, build 7601).