virtualbox.org

At last the problem is solved.
Windows 7 Ultimate 64 bit has a registry entry that blocks the USB mounting in the VB Guest.
The solution is described in this Youtube video:

https://www.youtube.com/watch?v=WDAxrVzBTmM

Before editing the registry, export/backup the registry.
The Guest now sees all the USB devices that have been added in the settings.

Thank you all again for your efforts.

Instead of linking to a video that might be gone next week, why not just describe the solution here?

The video does not show the complete path so I was lucky to delete the "upperfilters" entry at this location:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Class\{36FC9E60-C465-11CF-8056-444553540000}

Use this with caution and make sure to export/backup the registry before making any changes.

I have had another look at the video and I managed to stop it at a view of the regedit window which shows the full path of the entry as above.

samtweet wrote:HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Control\Class\{36FC9E60-C465-11CF-8056-444553540000}

That should have been CurrentControlSet. And for a more detailed explanation, take a look at http://www.faqforge.com/windows/remove- ... windows-7/

It's a Windows problem in reality, but it's good to know.

I find the article highly suspect. Yes, a USB problem could be a bad driver... but it could be a million other things too. Also, Windows has GUIs for rolling back drivers, so why hack the registry for this?