Steps for reproduction:

1) Multi-monitor configuration, you start off with the secondary monitor disabled
2) Start SwingSet2 demo
3) Extend the desktop to the second monitor
4) Drag SwingSet2 demo to the second monitor
5) All menu drop downs, pop ups and tooltips still display in the primary window.
To fix the issue, shutdown demo and restart it.

Error is reproductible both in 1.5.0_x and 1.6.0_x versions.