Stuck graphics after using Firefox
My laptop has developed an unusual issue. After I play a flash video in Firefox the last frame rendered in the video will be 'stuck' on the display even after Firefox is terminated. By stuck I mean that it is left as an artifact on the screen, where some, but not all other graphics overlap it.
E.g. text in the terminal will get printed on top of the 'stuck' last video frame. This is not just a trivial problem as the stuck frame will not deteriorate as other graphics get printed on top of it, it gets repainted as if there were some process in the background that keeps refreshing it -- i.e. it does never go away, even though some other graphics are always displayed on top of it (such as text).
I have not recently made any modifications to the system such as graphics driver updates.
I have tried to reinstall flash, I have tried to reinstall Firefox, I have tried to downgrade my graphics driver.
I believe this issue might have something to do with hardware overlay, but I'm not sure. Some process has to tell X to repaint this graphic, I believe that perhaps it is the driver that is responsible for this as video is played by hardware overlay which is associated with the driver?
Does anyone know what causes this problem and how to deal with it?
This system is a standard x86 running Slackware 13.1.0 with Linux 2.6.38. It has an Nvidia 8600GT graphics card, I use the proprietary drivers from Nvidia and I have tried several versions, the problem persists.