Step to reproduce:
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1) Run the swingset2.
2) Select "Table Demo".
3) Sort any column. Assume first column. Observe that column header is selected & sort arrow button is seen above the column header (jdk 1.6.0_03_ae-b01).
4) Move the mouse pointer on the second column of the table, now the mouse rollover effect can be seen in the second column of the table. Now you can observe one pixel gap between sorted column (first column) & the mouse rollover effect column ( second column).

This can be seen very clearly in jdk 1.6.0_03_ae-b01. This is because of http://monaco.sfbay/detail.jsf?cr=6434444. After the fix the column header & sorting look very similar to native table. but before the fix the gap is not seen so clearly. It may be due to header size was big or sorted column header din't had the animation or selected effect.

I tested this on jdk1.6.0 & there update releases. I have attached the screen shot of th e same.