Updated to v. 4.3.30 & Shared Folders no longer work

[FrankBlank]

Recently updated to v. 4.3.30. On Win7 x64.
VirtualBox version 4.3.30 r101610
Oracle_VM_VirtualBox_Extension_Pack-4.3.30-101610.vbox-extpack installed
On Windows 7 64 bit host, Windows 8 and 10 32 bit guests.

Windows 8.1 is running a bit slowly, but seems to have functions intact. Specifically, it will access the Shared Folders set up on the host.

But Windows 10, both build 10159 and 10240 (final) will not. They throw the following error, in a box with the date and title
"File Folder : "\\VBOXserverName\SharedFolderName\FileName.xxx
Invalid value for registry."

Does anyone know if this is part of VB's problems with Win10? Or something specific to Win 10 itself?
Or something that has been fixed in VB version 5.0.2?

Thanks!