Menus not opening on drag-and-drop

I've just upgraded from a fairly old version (4.something, I forget which) to the latest version (5.6), and my TLB menus are no longer opening when I mouse-over them whilst trying to drag-and-drop into them. This is true whether dragging from explorer to TLB, or dragging between TLB menus. My windows version is XP Pro. Any ideas what might be wrong?

Please can you send me (support@tordex.com) the toolbar backup file. I can't to reproduce this bug on my system, maybe something depends of your settings?

Also, do you use TLB on the taskbar or standalone?

I've sent you my toolbar backup file. In answer to your question, I use a TLB toolbar docked to the side of the screen, separate from the taskbar - although I've tried adding another toolbar to the taskbar, and had the same issue there.

Thank you for backup file. Unfortunately I can't to reproduce this bug. Are there are any visual effect when you drag the icons over the menu button? Maybe menu flashes, or cursor flashes?

Yes, the button is outlined in exactly the same way as when I mouse-over it normally. Also if I drag to a submenu of a menu that is already open, the submenu is highlighted just as it is when I mouse-over it without dragging anything. But the menus and submenus don't open to allow me to drop the item within them.

I can still successfully drag-and-drop an item onto the toolbar itself, or from a menu to its parent menus or to explorer - just not to a menu that isn't already open.