When dragging JOptionPane's JInternalFrame to the left the right part of this internal frame (one which appears in result of dragging) is trashed.

Couple of notices:

1) presence of scroll pane seems to be crucial (and that's why I'm adding huge JLabel);

2) one should drag the frame slowly, actually degree of corruption depends on the speed of dragging.

Sorry for complicated hierarchy: it emulates hierarchy of AGUI (JSR-209) TCK interactive tests.

BTW, for me the most probable place to fix is in DefaultDesktopManager.dragFrameFaster method. I'd especially suspect lines under "if ( !(visBounds.equals(previousBounds)) ) {". And it's quite probable that it's related to double buffering as well. Sorry that I didn't investigate this issue further.

And the last notice: it's reporoducible under 1.4.2 (1.4.2_10) as well. All on windows (xp)---didn't test other platforms.