Happens on OS X, but not Windows.

1. Hover mouse over a QLineEdit (notice I-beam cursor)
2. Right-click to bring up context menu (at this point, the cursor usually switches to the regular arrow cursor, although not always)
3. Take extra-special care to not move the mouse over the context menu
4. Hit [esc] to dismiss context menu
=> Cursor remains as the arrow cursor! It should switch back to the I-beam cursor. It won't switch back to the I-beam cursor until you mouse away from the widget and back on.

This happens with any widget that sets a cursor – e.g., spin boxes, date time fields, as well as any user-made widget that sets a cursor.