Problem showing 2nd level context menu on Windows 7/IE8

[puco]

When right clicking to show context menu in table and navigating on an menu item that has a submenu (e.g. Row, Column, Cell) the submenu ist rendered correctly but renders only a white rectangle without any content. Then after clicking on the rectangle the menu is rendered correctly

Step to reproduce:

1. Open FCKeditor demo (stable or current nightly)
2. Insert a table with default settings (using toolbar)
3. Right click into any cell to bring up context menu
4. Navigate onto Cell menu item

Workaround: Click into non-rendered area of the menu to render it completely

Environment: Windows 7 RC fully pached with MS IE 8 (8.0.7100)

Other: The editor works flawlessly on IE 8 on older Windows OSs (e.g. IE 8.0.6001.18702 on Windows Server 2003)

[Alfonso Martínez de Lizarrondo]

dup of #3293