Welcome back vdongen
We have looked into this issue, and as Markham stated before this is a very rare issue indeed.
Usually happening when Circle Dock starts.
Even I get it occasionally. To correct this, simply hide and un-hide Circle Dock.
Everything should come together as needed.
This is not to say that the issue has been ignored, rather there is no known solution at this time, and from what we have seen there may not be one, as it may be in the way that windows is handling the graphics build. Could be wrong
This has been a small end recurring problem since the original programmer.
there is no evidence of program instability nor does it appear that this will cause a system slowdown or crash.
Therefore this is simply a graphics bug
By the way; what OS are you utilizing????
I almost want to bet money that you are on Windows Vista, or a direct update from Vista to 7 without a clean install of Windows & OS