Steps to reproduce )

Use the following instructions to reproduce the problem:

0) Execute Qt Designer and open attached table_in_tab.ui.
1) Select "Tab 2". ( IMPORTANT : If you select "Tab 1", this issue can not reproduce.)
2) Select TableWidget in "Tab 2".
3) Display "Header/horizontalHeaderVisible" property in "Property Editor". It's default status.
4) Turn off value(check box) of "horizontalHeaderVisible" property.
5) Turn on value(check box) of "horizontalHeaderVisible" property again. It's not default status. The appearance of "horizontalHeaderVisible" is bold.
6) Save.
7) Reopen table_in_tab.ui.

[Result] The property of "horizontalHeaderVisible" is false unexpected.

This has been reproduced on Windows 7 and Windows Vista

When testing another on/off property - i.e showGrid on a table view, checking the box after unchecking it does restore the grid. With the horizontalHeaderVisible property, it is necessary to click on the "restore default" arrow icon which appears to the right of the entry field after changing the property to the non-default state.