Customize Menu Dropdown Not Showing

I'm running x32 SW2008-SP3.0 on an XP Pro x32 system, andwhen I RMB on an empty toolbar area and select the Customize Menuoption, the outline of the selection box flashes on-screen but thendisappears. This has only recently started happening.

Anyone else had this problem and found a solution?

I've already tried the registry reset trick and re-installing theVC driver.
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