Pressing the same Mnemonic twice brings up an incorrect sub-menu

I have added a menu 'Get' to the menu bar. 'Get' menu contains another sub-menu 'Get Messages For' and a menuitem 'Get Messages'. Mnemonics are assigned as follows:

'Get' - ALT + G
'Get Message For' - 'ALT + F'
'Get Messages' - 'ALT + M'

I am doing the following to reproduce the bug:

1. Press 'ALT + G' - Will open up 'Get' menu (Will have one menu item and one sub-menu).
2. Press 'ALT + F' - Will open up 'Get Messages For' sub-menu (this will have 2 menu items)
3. Press 'ALT + G' again - Will close the sub-menu and retain only the 'Get' menu.
*4. Press 'ALT + G' again - This will open up the sub-menu 'Get Messages For' whose mnemonic is actually ALT+F*

The last behavior (4) shown above is a buggy behavior since ALT+G is not supposed to open the sub-menu whose mnemonic is ALT+F.

This is reproducible on SolSparc10, WinXP with Tiger-FCS as well as Mustang. Run the attached test and follow the steps mentioned above.