creating directories with umlauts in a shared folder fail with error 0x80070057 on Windows Host

A) cannot create folders with umlauts in a shared folder within a Windows Server 2008 guest. (probably windows guest in general...)

If I try to create an "umlaut folder" within Gentoo guests, which have access to this folder via NFS , there are no problems and the folder is properly created. Also on the host (Gentoo) the folder-name is correctly written in umlauts. (all systems UTF-8)

B) this linux-host-created umlaut-folder is not listed when I refresh the shared folder view in the windows host....

log says nothing related, just: 00:00:01.461 SharedFolders host service: adding host mapping. 00:00:01.461 Host path /mnt/VIRTUAL/EXCHANGE, map name EXCHANGE, writable 1 00:00:01.461 SharedFolders host service: add mapping result VINF_SUCCESS 00:00:01.461 SharedFolders host service: adding host mapping.

I'm using virtualbox-bin 3.0.2

HOST: srv1 ~ # eix virtualbox [U] app-emulation/virtualbox-bin

Available versions: 1.6.6!f (~)3.0.4+i!m {additions chm headless sdk vboxwebsrv} Installed versions: 3.0.2!s(19:32:09 24.07.2009)(additions chm -headless -sdk -vboxwebsrv) Homepage: ​http://www.virtualbox.org/ Description: Family of powerful x86 virtualization products for enterprise as well as home use

[U] app-emulation/virtualbox-modules

Available versions: 1.6.6 1.6.6-r1 (~)3.0.4 {kernel_linux} Installed versions: 3.0.2(19:30:22 24.07.2009)(kernel_linux) Homepage: ​http://www.virtualbox.org/ Description: Kernel Modules for Virtualbox

GUESTS:

web1 EXCHANGE # eix virtualbox [I] app-emulation/virtualbox-guest-additions

Available versions: 1.6.6 (~)1.6.6-r1 (~)2.1.4 (~)2.2.0 (~)2.2.2 (~)2.2.4 (~)3.0.2 {X} Installed versions: 3.0.2(03:03:35 23.07.2009)(kernel_linux -X) Homepage: ​http://www.virtualbox.org/ Description: VirtualBox kernel modules and user-space tools for Linux guests

Is this a known problem , since in virtualbox's change-logs I could not find any fixes ?! Also when searching internet and your bug-reports I could'nt find a similar issue ?!