MacOS X 10.7.4 macmini4,1 7u6 b19,20
Add a JTextArea to a JScrollPane. Add a really long line so that scroll thumb moves to the end (i.e. to the right for European scripts). The caret would disappear as if under the right vertical scrollbar.
Note it should be the very last line.

Perhaps a similar bug, in that regard, was 4776535 long ago.