REGRESSION : painting artifacts is seen when switching between LinearGradient & RadialGradient

I have a stage which contains few controls that represents the attributes of Linear & Radial gradients. When the stage is visible. I see a Linear gradient is applied to a rectangle. When i switch between the linear & radial gradient applied to the rectangle using the radio button. i see a painting artifacts on top of the upper side of the rectangle. This happens only when jdk6u12 b04 is used, it works fine with jdk6u10 . Hence its a regression when using java. I tested this with javafx sdk 1.1_b09. I have attached the screen shot of the issues.

Step to reproduce:-
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1) Run the attached testcase. You will see a rectangle which is filled with linear gradient. Observe that when the stage is visible , the last color ( green ) is seen for some micro seconds like a flash.
2) Press on the Radial gradient radio button & move the mouse away from the radio button. You will the last stop color ( green color ) above the rectangle & other gradient colors. If you see the same then first issue of the bug is reproduced. This looks an extra green rectangle is drawn.
3) Click on the radial gradient radio button & back to the linear gradient radio button. Observe on upper side of the rectangle painting artifacts is seen. If you see the same , then the bug is reproduced.