After upgrading to 11.04 I noticed that in some online flash games like Cursed Treasure the active area of the buttons is not located any longer on the graphic of the button but is randomly off. This means if I go with the mouse on the button it isn't highlighted and a mouse click does not active it. I have to search around the button to find the active area. Also when I try to place towers on the game field (its a TD game) then I can also notice an offset. It seems that the mouse courser is not at the position as it is displayed.
The offset is changing after the browser window containing the flash game is scrolled up or down a little. This seems to be similar to Strange "gap" at the top of windows when first opened?, but also happens when the window is displayed correctly.
I'm using the 64-bit version of Ubuntu 11.04 with the normal Firefox 4.0.1. I installed the 64-bit Adobe flash plugin with the version 10,3,162,29 from the Adobe website by copying the plugin to the correct position.