When a Custom Render Jcombobox is added to the JToolbar , the combobox is not incorrect. I have two issues .
1)The arrow button of the combobox is incorrect.
2)Left side of the popup is 1 to 2 pixel towards the right & this is seen only in 6u10 b07 onwards. As it works correctly in 6u10 b06 & fail in 6u10 b07. Hence its a regression. I have attached the screen shot ( IncorrectComboBoxPopup.PNG).
There were similar kind of bugs , but they both got fixed. But still it can be seen on the JToolbar.

Step to reproduce:-
-------------------
1) Run the attached testcase. observe the arrow button of JcomboBox which is in the south of the frame. The button is incorrect. Click on the Jcombobox & observe towards the left side of the popup menu it is shifted 1 to 2 pixel right. If you observe the same then the bug is reproduced.
I even tested the same in 6u10 b08 pit build. Even there also i saw the same.