Unusable slow UI sidebar, lenses etc

I have a netbook with a dual core atom CPU and intel graphics (a samsung NC10) with 2 GB RAM. It was working perfectly with Ubuntu 13.04. However, in Ubuntu 13.10 the performance of the UI decreased significantly.

If I open the sidebar (moving mouse to the left) and move the mouse over the icons a tool tip appears. In 13.04 this tool tip appears promptly. In 13.10 it can take up to 20 seconds to appear. When then the mouse is moved to the next icon, it happens again. The worst thing I can do is clicking on the lenses icon (top most icon), which then tries to open the lens, which takes ages to open. To be precise, I killed compiz when accidentally when I click on the search. I tried waiting for 20 minutes, but that seams to be not enough time to open the lens. System load during this opening operation is close to 100%.

If I try to shutdown the system, and click in the system menu on shutdown a dialog should pop up in the center of the screen. However, this thing takes at least 5-10 minutes to open and be clickable. CPU load is also at 100%.

I assume that this might be some bug in the rendering engine. I don't think that it is a problem with software rendering, because such CPU based rendering should be faster than less then 1 frame per second.

I would like to help to debug this issue, however, as I am not a compiz and unity developer, I do not have any useful approach available.