I have the last version of Chrome 5.0.xx. and my Ubuntu is also of the last version 10.04. What I usually do is to open two instances of Chrome and divide the screen into two parts. In one part my son watches cartoons in Youtube and in the other part I just read some news.
So, sometimes, when I close some pages of the news I have being read the video which was being played in youtube crashes and immediately stops. I need to refresh youtube page and see the video again.
What is the problem? How to solve it
The problem is most likely caused by the flash plugin crashing. Chrome is protected through separation from crashing itself, but the effect is visible the way you described. Since Flash player is proprietary software, there is no way to directly fix the problem. Although there are numerous workarounds floating around the internet. None of these workarounds are complete fixes and only fix specific issues.
More generic solution is to utilize the HTML5 feature of chrome. Various websites allow one to enable the HTML5 features. Youtube can be HTML5 enabled here: http://youtube.com/html5
There are also HTML5 enabling extensions for chrome that convert embedded videos to HTML5 elements where applicable and so reduce the amount of flash elements in websites.
Chrome (and chromium) does a lot of threading (runs multiple processes), one or two processes for rendering and javascript (maybe more if you have a lot of open windows), and other processes for window management, gapping input and so on. When the render crashes all the windows (or tabs) that this render was in charge of will crash and chrome will show the "Aw, Snap!" page. It can be caused by a lot of things but basically means that a render thread has crashed. It might be a flash problem and it might be some fatal error in rendering html javascript ect.
Flash might also be the problem, but it might as well be that chrome doesn't yes fully support the flash plugin - If firefox doesn't crash at the same pages it's properly not a flash bug since they use the same plugin.
If you use chromium remember to report bugs ;)
I run Firefox if I plan on using flash-heavy stuff like Youtube or Homestar Runner, or if flash crashes while I'm using Chrome. It's pretty much the only time I use Firefox any more, but the workaround does the job for me. I'm open to any other solutions, though.