I also had this problem which I can fix by disabling compiz. I'm also on 32-bit Ubuntu so it isn't 64-bit related.
There's a semi-workaround here -> http://ubuntuforums.org/showthread.php?t=1275500&page=2 that doesn't involve disabling compiz which may help someone see what the problem is:
"Hold down the right button. Keep holding it down. Then left click somewhere on the page to get rid of the context menu. Now, still holding the right button, left click on flash buttons, etc. It should work."
I also had this problem which I can fix by disabling compiz. I'm also on 32-bit Ubuntu so it isn't 64-bit related.
There's a semi-workaround here -> http:// ubuntuforums. org/showthread. php?t=1275500& page=2 that doesn't involve disabling compiz which may help someone see what the problem is:
"Hold down the right button. Keep holding it down. Then left click somewhere on the page to get rid of the context menu. Now, still holding the right button, left click on flash buttons, etc. It should work."